Heating and Air Conditioning

Leaking Sound from Heater Controls. [John Sargent] One of my 740s made a hissing sound from under the dash in the area of the heater temperature control lever. The manual heater control assembly supplies vacuum to the under hood heater valve to shut off coolant flow to the heater core in the cold position of the control lever. The vacuum connection had come off the heater valve, and the free flow of air caused the hissing sound at the heater control. Connecting the vacuum hose to the heater valve cured the hissing sound, and shut off the flow of coolant through the heater core. See also the notes below under Vacuum Check Valves. See instructions for help on removing the vacuum hoses at the back. This rear connection has been known to leak.

That vacuum leak is almost certainly your floor/defrost diaphragm. It is on the left side of case just above the accelerator pedal. This diaphragm unit is double acting, i.e. it has vacuum to pull it both ways, blue hose for defrost and yellow for floor. There is a boot that seals the side that yellow hose applies vacuum to and when this boot goes bad it leaks when you use a/c or floor settings. It is a HARD job to replace this diaphragm unit. It requires removing a lot of under dash parts and ducts and then standing on your head to reach two extremely hard to get at nuts. I would try blocking the yellow hose with an old style fuse (the glass w/ metal end cap kind) and see if you notice any real compromise in operation, you won't ever get the full flow to floor and you'll always have some air out of defrost any time that you aren't on a/c. Climate Control Check Valves

[Inquiry] I have a 1990 760T and the H/AC is losing vacuum during low vacuum and during boost from the turbo. There is a tee above the intake that has two black & white fitting that connect to two smaller hoses that go to the fire wall. I suspect these supply vaccum to the H/AC but does anyone know if these are actual check valves to prevent loose of vacuum or boost from entering the system?

[Response: RL] There are numerous sources of potential vacuum leak (including some of the vacuum motors (bellows) on the actual heat AC system) but those two valves are a common problem. They are check valves to prevent lose of vacuum and if you bench-test them individually, you may find that they perform well under a fair amount of vacuum but that as soon as you try minimal vacuum, the valves will give up. You may try cleaning them out in WD40 or some rubber-softening substance but failing that, your best bet is probably an OEM replacement.

[Tip: Chris de Courcy-Bower ] If the air conditioning misbehaves and hisses when accelerating, check the two one-way valves that connect the climate control system vacuum pipes to the inlet manifold. If they let ANY air through in the from manifold direction when you gently blow into them then replace them. (The good news is they are cheap)

[John Sargent] The two black and white check valves are shown in the picture to the right. The car is a 1988 760T but most are similar. One hose is for the ACC, and the other is for the temperature sniffer in the dome light (if so equipped). I found that the hoses leaked at the check valves and using the small worm drive hose clamps took care of the leaks. Prior to that the panel vents would snap shut as soon as you depressed the gas pedal

[Inquiry] My heater won't shut off. When is the hot water control valve in the engine compartment shut off?

[Response] Vacuum to close the water valve is only applied in max AC mode or when the MCC temperature selector is fully cold. This varies according to the type of control system in the car (MCC, ACC, ECC) and the Volvo OEM service manual should be consulted for details of vacuum signals.

[Inquiry:] The heater in my 745TD still thinks it's summer... The engine itself heats up in a normal period of time, coolant temperature is at a normal level. The coolant system builds up pressure in the expansion tank. This morning I put a piece of cardboard in front of the radiator. I still got cold feet, so the thermostat is OK, right? The hoses that go towards the heating element are fairly warm. The air from the top dash vents is not very warm and even on position 4 the flow is rather weak. The middle vents are warmer and the flowrate is good. The flowrate below is nearly neglible and the temperature is just above 0 C.

[Tip from John Sargent] 700 series, with manual temperature selection, have a reputation for not being able to completely shut off all of the warm air when the manual temperature selector is fully off. The problem is the flapper door in the heater is not fully closed. There is an adjustment for this in the cable, just behind the heater control. If you remove the glove compartment, you can see the heater controls. The cable on the bottom controls the flapper valve for heat. The adjustable part of the cable is at the heater control. If you see a larger part of the cable, about 3/8 inch and about 2 inches long, that is it. Turn that larger part of the cable until you can feel the temperature control knob moving off of its left hand stop. You are done!

[Inquiry:] I guess that the heater core in my 86 740 Turbo wagon is leaking cause I have antifreeze on the front floor. Heater Core for air conditioned cars

Is this as nasty a job as it looks?

[Response:] Try to find out where the coolant is coming from. Usually if the core goes bad you get a coolant mist on the windshield with the defrosters on and you can get some coolant drainage from the A/C condensate line or onto the carpets. As a temporary fix, you can add a stop leak additive to the cooling system. But plan on a new core soon.

[Editor] Note that air conditioned cars do not have hoses or a water valve inside the passenger compartment. Cars with heater only have a water valve on the left side of the console against the firewall inside the passenger compartment and this can leak, appearing as though the core is leaking.

Heater Core Replacement: See the separate FAQ file which explains the replacement procedure for the Manual Climate Control-equipped car. ACC and ECC are similar. [Tips from Bob] I have done 2 heater cores on 700 series cars. It is very labor intensive. You have to take apart the lower half of the dash and partially disassemble the heater case. The heater core is on the left lower side of the case. You need to remove radio, fusebox, left side center console panel, bracket that holds fusebox,bottom left side air distributon box. When you can finally see the heater core, it looks like a hand grenade went off in your car. If you are not familiar with the procedure, plan on a weekend. You MUST have a good shop manual. I strongly recommend getting the Volvo OEM climate unit manual (see Volvo Technical Literature.)

[Jim Parker] When I replaced the heater hoses, I gouged the surface of the brass core nipples with a razor knife or screw driver when cutting and prying off old hoses. The new hose was pushed up tight against the fire wall that has a opening around the nipple filled with a porous rubber sponge, where it leaked. I pressure tested my core before pulling it and it held pressure! So I sanded/cleaned the nipples and reinstalled hoses, which sealed the second time and my leak/problem was cured.

Water Valve Replacement. The heater water valve controls the flow of coolant to the heater core. If this plastic-bodied unit cracks, you will instantly lose a majority of your coolant. The engine-side valves installed in air conditioned cars are exposed to much more heat and have a shorter lifespan than the passenger-side valves in heater-only cars. The engine-side units last about eight years and should then be discarded. When you replace this, consider new heater hoses as well. Heater Water Valve for AC-Equipped Cars

For Air Conditioned Cars: The heater water valve is installed in the engine compartment, right near the top of the transmission fill tube and under the intake manifold near the firewall. It's hard to see it and the area is crowded: best to feel down the bottom heater hose until you find it. To replace:

For Heater-Only Cars: The heater water valve is installed in the left side footwell, up near the left edge of the center console behind the kickpanel. It is mounted to a plate on the firewall. It is round with a hose entering it from the heater core.

Make sure that the heater hoses are held by the plastic clips that keep them away from the block, the EGR system, and other areas they can wear and leak.

[Inquiry] I have black foam blowing out my vents. What do I need to do to fix this?

[Response: David] This comes from deteriorating foam sheets on air doors within the system. I popped all the air direction vents out with a small flat tip screwdriver. There are only two small nipples (one on each side) holding the vents in place. A little leverage and they come out easily. (BE CAREFUL!!! THE SMALL CURVED WASHERS THAT PROVIDE THE TENSION TO HOLD THE VENTS IN POSITION AREN'T ATTACHED TO ANYTHING!!!). I figured I could snake a small piece of garden hose taped to my shop vac and suck the stuff out. I cranked the A/C on high recirc and all the stuff just blew out. Didn't even get a chance to test the garden hose vac! Left the vents out for a couple of more weeks just to make sure there were no late arrivals. Armor All'd the vents and put them back in. No problem since.

[Response: Wong] I closed all the vents except one. Put the blower motor on the highest setting. Maybe if you turn the heat on it would help even more. Then stick a vacuum cleaner up to the vent and suck that crap out. Should take a few seconds. Use a little pick to help get some of the foam thru the vent slots. Move around and do the other vents one at a time.

Repair or Replace? If your motor is squeeking, you might be able to oil the bearings but most 740/940 motors have sealed and inaccessible bearings. Plan on a replacement motor.

[Tip from John McIntosh] It is quite easy to dismantle the motor by bending the tabs holding it together. Mine had been squealing and making sundry horrible noises. The rotor was encrusted with iron filings and the bearings were dry. I lubed the bearings with 3 in 1 soaking the felts, blew off the iron filings. Mounted the rotor in my drill chuck and filed the armature with a smooth flat file, finally polishing with glass paper (not emery which I am told is conductive). The hardest part of re-assembly is ensuring the brushes are held back whilst the armature is put in place. This was done using pieces of wire. Dont forget the cooling pipe when re-installing. My fan motor now runs silently and well.

[Response: Kevin Lawler] If you have done several 240's you should be able to do a 740 blower motor with your eyes closed! Remove the under dash hush panel on the passenger side. Next remove the right side kick panel over the fuel ecu, then remove the 2 screws holding the ecu and remove the ecu. next remove the 3 screws holding the ECU bracket, and remove the bracket. Now remove the 3 or 5 screws holding the blower motor in place and remove the blower motor. Remove the ground wire from the old motor if so equipped and unplug the power wire or the connector. Install new motor in reverse order. Some cutting and modification may be required depending on the style of the motor. I had to rewire the connector with a soldering iron, but that was no big deal. I have done several of these, always in less than 1 Hr.

[Response: Ney] The only important tip is to remember to disconnect the battery, because the ECU may need to be removed in order to gain access to the blower. Also remember the small black wire with self-tapping screw is ground on the single-connector motors. Newer motors are dual-prong.

[Karl Siegler] Make sure any dirt and dust caked on the fan is removed as even a little build up will cause the fan to be out of balance and thus reduce the life of the blower motor. Some soaking in hot soapy water and an old tooth brush completed the job; be careful not to disturb the balance clips.

[Response: Gary Defrancesco] In the last 6 months, I have replaced the blower motors in both of my late '80s vintage 745Ts. The replacement kits came from IPD and include the adaptor ring required to mount the new blower to the heater/AC box. Apparently Volvo made a design change in the motors and the replacement ones require a slight mod to the box. In fact the IPD kit contained the part from Volvo for the mod. TheVolvo shop manual also describes the mod, so I am convinced it is a Volvo design change and not an aftermarket attempt to make a universal motor fit a Volvo. My '87 745T apparently had already eaten a motor and the mod had already been made. So replacing this motor was a piece of cake. My '88 745T had not had its motor replaced, so I had to do the mod. Follow the above procedure and read the directions for the modified mounting plate that came with the motor. You may need to cut off a short plastic drain pipe using a hack saw blade, apply some sealant to the adaptor ring, screw it in place, and drill a vent hole. No big deal. Then mount the new motor, solder the wires, and close everything up.

[Tip from Jarrod Stenberg] If your blower motor dies, it can take the resistor pack with it by causing overcurrent through the resistors. Make sure your heater control runs the motor correctly at all the settings from "off" to "high": if it doesn't, replace the resistor assembly. This is located right next to the motor on the air plenum.

760 with ECC; 960; S/V90 Blower Motor Replacement. Remove the battery ground lead, the passenger kick panel, the glove box, the kick panel in front of the door, the a/c ductwork, the bracing/crashbar (left bolts remove easiest from radio compartment)and the right crashbar mount. Remove the terminal strip and bracket holding the back of the motor, then the electrical connector and the motor itself. When reinstalling, don't forget the rubber gasket around the housing. The vent system in the 960 can suck paper and debris very easily when in recirculation mode. It usually ends up inside the blower motor assembly, located underneath or behind the glove box. Get used to removing the blower motor to retrieve the debris from the inside of the squirrel cage. You'll probably be surprised at what else you find in there.

[Inquiry] Several days ago my blower/fan motor stopped working. It works on the highest setting which is number 5 but does not work on the lower settings. Local dealership Heater Blower Motor Resistor Control

diagnosed a failed resistor that they determined was faulty in the motor.

[Response: Warren Bain] Probably a failed resistor pack. Remove the lower panel under the glove box, remove the glove box. There are two small covers on either side of the box with screws under them. The resistor pack is attached to the plenum with several wires close to the fan motor. Replace it. My car is 14 years old and has the original resistors. Make sure the blower motor works OK.

[Inquiry] Fan switch only works on 5, no 1,2,3,4,? Is it the switch or is there a resistor pack or can it be the motor?

[Response: Abe Crombie] There are two things that come to mind dependent on how a 92 is wired. There may be a blower relay on the case behind glove box. It passes all the current from resistor to blower but on high the relay is energized and its contact switches over and feeds direct 12 v to blower saving the switch from having to carry the high amperage. If the contacts on the lower speed side are burnt this failure would occur. The other is the resistor itself. I believe a 92 has this feature but it might not have occured until 93, anyway, the resistor may have a temp fuse integrated into it that will go open if the blower resistor has debris around it or if the blower motor drags. Either of these two will make the resistor get hot enough to trip the temp fuse. If the resistor has the temp fuse it will be a green ceramic covered resistor and the temp fuse will be adjacent to ceramic core. It is a silver 3/16" cylinder with tapered ends , one of which is white. In either case i can tell you w/o too much doubt that you will have to go behind glove box as the relay is there and the resistor is stuck into the blower case in that area also.

Replacement Blower Motors.
Pre-90 740 Cars: Earlier blower motors used generic units from GM. GM mid-80's blower motors for AC-equipped Chevy Citations are exact replacements. Another exact replacement is a Siemens-made replacement blower for a 1984 Chev Citation with the single power connection for use with air conditioning (Siemens part number is PM-105). Also: look for an '81 Olds Delta 88 w/ air conditioning blower motor.

Pre-90 760 Cars: The replacement for the 760 series fan motor is a standard GM fan motor; at NAPA the part number is 455-1076. I was shopping for a fan motor for a '87 760. The clerk responded, $57.94 and we'll have to order it. Then, I said ok, Try a '83 Chevy Impala with AC. In-stock and $17.99 with lifetime warranty. In all cases, you will have to reuse the blower cage.

Post 1990 740/940 Cars: A Factory Air #35339 that lists for $49.88 on the PartsAmerica website will fit with a different wiring pigtail made using an adaptor pigtail from a bit of heavy automotive wire and some female and male crimp on spade connectors. This will allow you to connect the original harness plug to the motor without hacking anything. Make sure the polarity is correct on installation so it does not run backwards. This is the same blower as used in any '91-'96 rear wheel drive full size General Motors car. Note that post-1990 cars use a different plastic mounting plate.

The reason the original fan failed became quite apparent in today's rain. Water showed up around the new fan. Apparently the 740 has a tendency to leak on the passenger's side with the water ending up in the plastic basin that the fan sets in. [Note: See Volvo TSB for a fix for this problem.] [Second Comment:] After posting an e-mail question regarding heater blower motors on the Swedishbricks mailing list, I received a response from Bill Cheb that he rebuilds heater blower motors and adds ball bearings which should add an extra several hundred thousand miles to their endurance. Bill was easily accessible via e-mail at bill.cheb@ualberta.ca. He promptly responded with information on how to order. His delivery was prompt and included detailed instructions on how to install the new motor. The total cost including delivery was $125.00.

960/90 Series Cars: I found what was supposed to be a replacement at Advance Auto Parts for $29. It was an exact fit mechanically but had the wrong electrical connector. I returned the motor and ordered one from FCPGroton for $60, which was the same motor with an additional electrical adapter to fit correctly.

Interior Water Leaks: Loose Water Shields/Clogged Ventilation/AC Drains. [Tips by Steve Seekins, courtesy of Guri Roesijadi] [Inquiry:] Water is leaking into my front footwells and soaking the carpets. How do I diagnose this? Location of Evaporator Drain

[Responses: Dave Stevens/Norm] The single most likely culprit for the wet carpets is a plugged evaporator drain - look on the firewall, passenger side - you should see the drain outlet there - may be flush with the firewall, or there may be a tube attached that runs down toward the frame rail. The plastic casting for the lower air-box half actually includes the drain spigot. It is likely clogged with leaf debris or other stuff.Suction it out by poking and then vacuuming. [Response] I found the drip tube grommet at firewall had deteriorated and cracked at bottom (probably due to heat/age).Lathered with silicone caulk inside and out. I suggest placing a small downspout tube to extend drip pipe as the drain only extends about 1/2" thru firewall and water was dripping out and running back inside firewall.

Check the air intake behind the hood - there should be a screen under the slots and bonded to the bottom of the slots. If it has come loose, it lets stuff into the air box. To repair, you need to remove the cowl piece -three bolts along front edge under rear edge of hood (no need to remove hood) and remove the wiper blades and rubber pieces. Middle bolt is usually hidden behind the rubber weather strip. Cowl moves forward and then pulls back off toward the windshield. There are pins on each side that fit into slots on the cowl. It also fits into clips along bottom edge of windshield. See the section in Electrical-Wipers. Getting the cowl back in is a bit more difficult than getting it out. First, often the small plastic pins at the ends break - they are sort of a blind plastic rivet affair - good to have one or two new ones on hand. Second, getting the cowl properly lodged under the clips at the lower edge of W/S can be tricky and if you don't, the cowl will not lay down against the lower edge of w/s properly. Push down on the cowl while a helper pushes back against the firewall edge.

The leaf screen is fastened to underside of cowl with sticky black adhesive caulk. The black glue can be replaced with Butyl Tape (3M WindowWeld Ribbon Tape in 1/4 inch diameter from an auto parts store) which is the stuff used to glue in an older windshield: this lasts forever. Duct mastic from a heating contractor might also work. Warming it up with a hair dryer will make it nice and sticky, then mash the screen into it. Place some pieces on to the screen and squeeze these into the screen so it will not fall down in hot weather. Wear gloves or use paint thinner to remove from your skin. Consider fastening the vent screen with 8 small zip-ties, since the mastic adhesive tends to soften and fail in summer heat. The cowl drains to each side, where leaves can accumulate and block water flow. Clean this out.

[Response: CW] If your water leak is on the right side then the shield over the air intake for the heater fan on the passenger's side could be loose. The shield is plastic and is underneath the cowl in front of the windshield. If the shield becomes detached from the window edge, the water runs right off the windshield and into the intake, down onto the blower motor and then on the floor. I had this problem on both my 745s. If this is your problem use the 3M WindowWeld tape noted above on the window edge of the shield to keep the water from getting in. Before you install this, clean off both surfaces with lacquer thinner.

PITA to try to dissassemble the air box, but you might try removing the blower motor (which may be trashed if the lower bearing has been running in water!). Blower is held in with 4 or 5 screws, one electrical connector, ground lead, and there is a motor cooling air tube. Motor housing is usually sealed with RTV to prevent any air leaks. To get it out, remove panel above passenger feet, remove the right side hard panel, unplug and remove computer and the computer bracket. You should now have enough space to get it out - 8mm nut driver on flex extension is helpful. Remove the tube from the motor housing and inspect the lower bearing - any signs of water or rust in there likely means lower bearing is trashed and motor will soon fail. Then use air nozzle to blow in to the drain and force any debris/leaves out through the blower motor hole, or try clearing with piece of coat hanger. Just be careful not to damage the A/C unit inside. Of course, the air method may only move the debris away from the drain temporarily. [Editor's Note:] Check that the blower motor mount in the air plenum is not cracked.

Front Footwell Vent Seals. See the FAQ section describing leaks at the seals behind the front footwell vent panel covers. These can leak and soak the carpets.

Basic A/C Operation Information and Safety Caveats. [Chris Herbst] A/C does differ between RWD models, so it is important to relay the CORRECT information about which side of a particular system the components are on. Don't up getting something backwards, or reading high pressure on the low pressure side and overcharging (and exploding) a system. And possibly getting hurt in the process. For these reasons, it is HIGHLY recommended that anyone who is unsure of what kind of system they are working on, stops and either figures out what it is, or abandons the job until they can figure it out. Also it would probably be good for people who are confused about these differences, to STOP giving advice before someone destroys their A/C or gets injured. This is a review of systems on the 740/ 940. The 940 information applies to certain models as noted in the section labeled 940. Models are listed by vehicle model because most of the confusion I have seen is primarily caused by people applying 240 TVX A/C information to 940 CCOT A/C systems. Included at the end of the review is a breakdown by model. Information on model years is stipulated when known to be true; otherwise model information is suggested as being possibly earlier or possibly all models because of the inability to verify this information at the time of writing. Model years are included where known. The purpose of this review is not to include every screw, pipe, and switch in the A/C system, but is merely to educate about the fundamentals of two different kinds of A/C system found in RWD Volvo models from the mid-1980s to 1998.

940 Models This system also applies to 700 series cars and 960 models. It also applies to *ALL* 240 models from 1991-1993. The mechanics of the system are the same between climate controlled and non-climate controlled systems; electronics vary and are beyond the information covered in this review. The 900 system is a clutch cycling orifice tube system, abbreviated CCOT. The CCOT system cycles refrigerant through the following components:

The CCOT system has the accumulator-dryer (large silver can at the firewall) on the LOW PRESSURE SIDE. It is suitable to charge into the accumulator, as is plainly evidenced by the presence of a charge valve attached to the same low side pipe adjacent to the accumulator. Again, it is STRONGLY recommended that anyone who is unsure about the components of an A/C system, avoid work until a time at which they have become sure about it. Damage to the system, and injury can result. Verify all information before attempting any air conditioning repair or maintenance. As a review, here is a breakdown by model: CCOT systems (GM-type) 240 1991-1993 ONLY; 740 1988- (unable to verify, should be all 740 models); 760 1988- (unable to verify, should be all 760 models); 940 all; 960 all; S90/V90 all.

Recommended System Maintenance When the System is Open. As soon as you have warm weather, evacuate your A/C, raise the front of the car, remove the air guide (not engine pan) and front grille. Disconnect and mark or identify the three connectors at the bottom of the condenser on the passenger side. Unbolt the lines in and out of the condenser. Cap or cover with tape those lines to keep air and humidity from entering the system. Undo the clamps that hold the radiator in place, push the condenser up from its moorings and pull it out from under the car. Undo the screws that hold those plates at the bottom of the condenser and put plastic or rubber plates between the steel plates and the condenser to keep metal to metal contact between steel and aluminum. Perhaps the plastic-like shims that come with Volvo rear brake pads will do the trick. This is a good time to flush that condenser before you put it back in the car. While you are under the car, you may want to remove the engine pan and take out the A/C compressor to flush it and refill it with fresh oil. Sanden specifies Sanden SP-20 oil (8.45 ounces), but I think this is PAG 100 oil, perhaps with additives. Eight ounces of PAG 100 should do in a pinch to refill the compressor. Taking the compressor out is not bad if done from under the car. If possible, put in an Airsept screen in the suction line at the compressor. Airsept has illustrated instructions at its website. Check and replace the orifice valve in the high pressure line connection on the passenger side, not at the evaporator connection. Perhaps a variable orifice valve is called for, but I get 32-34 degrees Farenheit air at the vents with the factory orifice valve. Change the accumulator if it has been there for several years or many miles or lines were left open more than ten minutes so air got in. Otherwise, Volvo says it can be changed every second or third time you open the A/C lines. Put in at every connection you open brand new R134 O rings (yellow, not black) lubricated with either mineral oil or an application-specific, silicone-based lubricant instead of PAG or POE oils. (PAG or POE oils should not be used due to their hygroscopic nature that can promote moisture attraction, possibly causing o-ring deterioration or thread fitting seizure.) Draw a vacuum of 29.7+ inches of mercury for at least an hour. Check that the system maintains that vacuum after you turn off the vacuum pump. If you use Johnsen's R134 refrigerant in liquid form (you turn the can upside down rather than hold it upright like with Dupont Sava R134) preferably with UV dye, the vacuum in the system sucks in a can or two right away. As soon as you start the engine, suction from the compressor will suck a third can. That is 36 ounces rather than the 32 ounces called for the A/C on the 960. That works for me, but I remember Tom Irwin recommends a small food scale to put in exactly 32 ounces of R134. If you have to change the condenser, I found the direct fit aftermarket one from FCPGroton has the advantage over the condenser that was in the car (Volvo?) of no steel plates against the aluminum. Otherwise, that aftermarket condenser is a bit shorter top to bottom than the one that was in the car, with round rather than flat tubing. I cannot compare capacity (BTU) between the two condensers, but so far that aftermarket unit gives me 32-34 degrees Farenheit air at the vents in the tropics!

Useful Air Conditioning Parts, Products and Tools. AScanTech (Avantia) direct fit aftermarket condenser is $175 from fcpgroton and a Volvo one is $439 from Swedish Engineering. A new (not remanufactured) Sanden SD7H15 compressor is $320 from FCPGroton. Locally, I was quoted $995 (yes, $995) sight unseen so I do not know whether it was new or remanufactured. An accumulator will cost you $50 from FCPGroton and maybe a couple of dollars more from Swedish Engineering. A Mastercool flush gun is $43 and flushing solvent is $20 a bottle from www.ackits.com You will need shop air to use those. The Airsept kit with screens to keep debris in the system from getting into your new compressor costs $67 from www.jcsonlinetoolshed.com. For leak detection, get an Airmax LED penlight for UV leak detection from http://www.keep-it-kool.com(costs about $40) and a set of UV-enhancing glasses from JC Whitney for about $5. You can purchase air conditioning dye injectors from NAPA. The glasses are necessary to see the dye. To seal pipe joints with o-rings, get some Nylog, which is compatible with the o-ring material and prevents corrosion.

[Inquiry:] I have a 1993 945 turbo. The air conditioner (134a) works ok on the highway. when it is less than 90 degrees outside, but only makes the car bearable in city driving. I checked the charge level and it appears to be fine. Does anyone have any ideas?

[Response: Abe Crombie] I had a car like yours and the a/c was fine in the southeast US summer. The problem could be any one of several possibilities like heater valve not being closed at full cold position of the temperature control, partially blocked condenser, cooling fans not working correctly, etc. The only way to know you have the right charge level is to recover and then refill a/c system. The hot water valve should be getting vacuum via a vacuum switch on the heater control when the temperature knob is turned that last little bump to the left. Bugs and stuff will block the condenser over time and this will make performance suffer even more on R134a systems. The electric fans must work properly for the same reasons.

[Inquiry] Need help with my '91 740 Turbo Wagon A/C system. It works great when I'm on the highway (ie. speed greater than 40 mph) but when I slow down or stop I lose cooling. I believe that I am not getting good condensing action even though there is a belt driven fan on the engine. I suspect that the small electric fan in front of the radiator needs to come on with the A/C

[Response: Rob Bareiss/Norm Cook]If you have one electric fan and no booster as in the 940 cars, then it is supposed to be on AT ALL TIMES when the AC is running. If you have two fans (a belt-driven main fan with an electric a/c booster fan in front), you will find that the booster fan is thermostatically controlled. My guess is if you pull your grille out, and reach in there to test the booster fan, you'll find it does not turn freely. So the motor probably burned out when it seized up. Just had three of them do that, all on 740's like yours. A good used one can likely be found at a junkyard- new one is $211 from Volvo (!!!!). It's probably worthwhile to have your AC system leak checked now as well- if it's leaking at all, consider a conversion kit to R134 refrigerant. It's at the point now that it's almost cheaper to convert it than to recharge with R12. A kit costs $61 from Volvo, and R134 ought to be less than $50. If your system was fully discharged, a full charge of R12 would be over $110. A partial charge would be cheaper, and since yours works mostly, it's probably got close to a full charge in it. Keep in mind also that you'll be getting a new expansion valve and receiver/dryer with the Volvo kit, so it ought to be pretty efficient for years.

Simple Leak Detection. Mix dishwashing detergent and water in a spray bottle and spray every connection. If your system has pressure, then soap bubbles will show the leaks. Look for an oil stain on the tubing or the connectors, since a leak will allow compressor oil to escape the system. More accurate leak detection may be made by injecting fluorescent dye into the system (no more than 1/4 ounce at a time and no more than twice) and using a UV lamp to look for leaks, by drawing a vacuum on the entire system and looking for loss of vacuum, or by using an a/c "sniffer" designed to detect the presence of refrigerants. If you inject a dye into an R134a system, make sure it meets the SAE

Control Unit PCB Solder Cracks. See the FAQ section describing common electrical failures in the heating/air conditioning system control units. These can be intermittent: sometimes teh a/c works fine, other times not.

[Inquiry:] Is it normal for the compressor to cycle on and off like this? The one on my wife's old Mitsubishi cycles on and off but it runs for a longer period of time than this one.

[Response: Chris Herbst] The clutch cycling orifice tube (CCOT) A/C systems such as the one in your Volvo are designed to cycle the compressor on and off to maintain a workable system pressure. While the thermal expansion valve systems in other cars vary other factors, the FOT (fixed orifice tube) needs to have the flow maintained at a steady pressure. That's why the pressostat is on the low side of your system. It senses when pressures are too low, and therefore too cold. It stops that to prevent icing. The reason for the frequent cycling of the compressor clutch is not dependent on only one factor. The clutch on the compressor will cycle when the refrigerant pressure drops to 25.

The pressostat causes the clutch to cycle. If the pressure is lower than about 20 on the low side (I prefer that to 25psi for better cooling with R134) then the evaporator will ice, as will the accumulator and its associated tubes. Then you've got no cooling at all, and the compressor will shut off. The compressor will cycle for the following reasons:

To put it all together, the system is cycled to maintain the most useful pressure for commonly encountered temperatures. With a FULL charge, the system will cycle very frequently in cooler temperatures, and sometimes will not have the pressure to EVER come on. That is how the CCOT systems work, and why they cycle the clutch a lot. The thermal expansion valve systems cycle the clutch less. If the charge is proper, in high temperatures, you might never see a time when the compressor clutch cycles off, until the cabin is cool, or the temperature drops outside. If the charge is too low, it'll cycle frequently to keep ice away.

If the charge is too high, you will blow the system up. That's why you need to know how much refrigerant is in the system. In very high ambient temperatures, it's occasionally advantageous to have a slightly low charge, only because the pressures of the system are maintained at a more optimum level despite the huge outside temperature differential. But that same system will be largely ineffective if the temperature is lower.

The whole picture is, you should make sure you have the proper charge as often as possible, especially if the system has a leak. That way, you'll be assured proper cooling, good compressor life, system integrity, and for you, sanity. Fortunately, A/C work is NOT very hard if you take the time to read about it a little bit and learn about what causes it to function as it does.

[Motor Magazine, Apr 03] A just-low R134 refrigerant charge (typically a 10% to 20% undercharge) significantly reduces oil flow, according to Four Seasons' Jim Johnson. He gave this example for 88 F ambient: The a/c duct temperature rose just 3 degrees (from 46 to 49F), hardly enough for a customer complaint. Yet so much oil was trapped in the evaporator under low-refrigerant conditions that oil circulation dropped from about 10% to 25% by weight to just 2% to 4%. That's a prescription for increased compressor wear and therefore short compressor life. Other causes of similarly low oil flow, he said, are internal restrictions (typically from contamination, which increases rapidly with low refrigerant), poor airflow through the condenser and high coolant temperatures.

93 and later models that have R134A refrigerant as factory fill have a compressor high temp shutdown switch at compressor clutch circuit on comp. This can make compressor go off for 5-10 minutes if one of two things is happening:

[Inquiry] My 960's a/c compressor cuts off during city driving when accelerating. When coasting or on the highway just maintaining speed, the a/c works great. The Volvo manual says it is a fuel economy issue whereby the a/c compressor cuts off during acceleration, but this should occur only at wide-open throttle.

[Responses] Problems are likely to be found in the vacuum system that controls the opening and closing of the flaps in the AC vent ducts; namely, the vacuum control check valves, diaphragms and/or defrost/floor vacuum motor, located just above the accelerator pedal, or in the integral vacuum reservoir built in to the evaporator case.

Faulty Control Unit. See the FAQ section below about solder failures in the control unit that can prevent the compressor from engaging.

Faulty Low-Pressure Switch. [Inquiry] When the A/C button is ON, my compressor is not engaging nor the cooling fan is coming ON. Supplied 12V to the contacts at the low pressure switch, (compressor did engage), charged the A/C to 30 PSI on the low side, installed the switch back, but again same thing as above.

[Response: Chris Hollis] I had the same problem with my '94 945T. You might A/C Receiver Dryer and Low Pressure Switch

check continuity of your low pressure switch: I had a bad low pressure switch. I bought TWO bad switches from Volvo, before I bought a third aftermarket switch from a place called The Volvo Site, part number 1343216. I forget the exact pressure ratings, but they switch off (open) around 20psi and back on (close) around 40 psi. The bad ones I got would switch open at around 20 psi then almost immediately close again. This caused the compressor to cycle faster that you could count. Trying to figure it out drove me nuts. [Editor] The location of the switch ("2" in the photo above) on the receiver-dryer ("1") makes it subject to damage when replacing distributor caps, etc. Unexplained compressor cycling when you know the system is charged should lead you to suspect a faulty low pressure switch.

Air Conditioning Leaks. [Tips from Chris Herbst/Paul Willems] The common freon leak spots are the condenser, any O-ring, suction line, and the high pressure pipe along the right side frame rail. The last one is the most common, because the rubber from the straps that hold it down deteriorates from engine heat, leaving a lovely condition for bimetallic corrosion. Some cars suffer from low pressure aluminum pipe leaks in the pipe beginning at the accumulator that dips down running along the passengers side before turning 90* and crossing above the splash pan (where it becomes a rubber hose) below the front of the engine again becoming an aluminum pipe where it connects to the compressor. The intake pre-heat shield or air intake tube rubs against the aluminum low pressure hose causing it to break through.

Leak Points . 960 Condenser Leaks. [Tip from Rafael Riverol] Markku from Finland reported epidemic corrosion of the A/C evaporator on '93-'95 cars due to lower corner attachments with steel bolts in direct contact with aluminum. As he reports it, iron in contact with aluminum in the presence of water and road salt corrodes the evaporators in four to six years. If your 960 is like mine, then the A/C condenser is held by bolted through steel plates touching the aluminum of the condenser which will corrode and leak refrigerant and PAG oil. This can ruin your compressor too and send debris through components and lines that will prove difficult or impossible to flush successfully before putting in a new compressor and condenser. BTW, To save all the trouble and expense of an A/C overhaul after your condenser corrodes and leaks, see if it is held by bolted through steel plates at the bottom both right and left sides. On the condenser in the 960,it is easy to take out the steel bolts and plates to replace them with aluminum, plastic or stainless steel bolts and nuts with plastic or aluminum shims between the steel plates and aluminum of the condenser body. That can be done by taking the condenser out of the car from below, or taking the radiator out of the car and working on the untouched condenser in place.

High Pressure Hose Bracket Wear Leaks. [Editor] There is on my 95 940 a high pressure a/c hose from the compressor to the condenser. Under the RF bumper, the hose terminates in an aluminum tube before connecting with the condenser. This tube is secured to the underbody with a vinyl-coated steel clip, which in my case rusted and wore through the aluminum tube causing a loss of R134. The hose assembly is expensive, so check the bracket and make sure it is not destroying your a/c hose/tube through corrosion.

Should I Use a Sealer? In a word, no. There are two types of sealers: stop-leak for perforation leaks and seal sweller for leaking O-rings and O-ring type gaskets. They're often combined in a single product. While the first will seal pinhole corrosion leaks, it won't seal anything else and because it works by reacting with moisture, it can clog up your system. The second can distort o-rings.

Should I Use Teflon Tape on Connections? Don't use Teflon tape. Refrigerant causes Teflon to soften and fray and little pieces will break off to clog the expansion device. The teflon tape will also buffer threaded connections to cause bridging [a gap]on a o-ring fastener and other types of compression seals. All sealing is accomplished by the o-rings, not the threaded connections which are only used to compress the o-rings.

Should I Use a Tracing UV Dye? Yes. If your system has a leak, using a UV dye will allow your tech to trace it that much more easily, especially the leaks that are intermittent or hidden. See Tools above for a source of UV lamps and detectors. If you do use a dye, add no more than 1/4 ounce at a time and only twice. More than that may dilute your compressor oil. If you inject a dye into an R134a system, make sure it meets the SAE J2297 standard for refrigerant and oil compatibility. One dose of dye is enough. Adding extra shots of dye not only won't help, but because dye changes the viscosity of the oil, excessive use can adversely affect compressor life.

[Inquiry] Can anyone tell me how to distinguish between the high and low side connection in order to recharge the air conditioning on my Volvo (1990 760, 4 cycl. turbo)

[Replies: Bob and JohnB] The flow in the system goes from the compressor under high pressure to the condensor. Then via the receiver/dryer to the evaporator inside the cabin. From there it flows at a low pressure (the suction side) back to the compressor. Locate , it'll be the low side. High side port is on the compressor, low side port near the hose from the firewall to the compressor on the big silver round cylindrical container (receiver/dryer). There should be a cap covering the low-pressure schrader valve. Don't do this unless you have a set of manifold gages so you can ascertain high and low side pressures. You should also have a digital thermometer to tell the cabin vent temp. Figure around 30-40 psi on low side and 150 or so on high side at 2000 rpm, 85F, system stabilized for 5-10 minutes, and inside cabin vent should run about 40-45F at recirc.

Recharge After R134 Conversion. [Inquiry] Can't I just use the $15 recharge kit from Walmart with the hoses and R134? [Tips from Chris Herbst/George Downs] The complete recharge system is the way to go if you want to destroy your A/C system. Topping off a system that has a leak is totally unscientific and will yield less-than-optimal performance.

System Pressures. For a chart to compare system pressures at ambient conditions using various refrigerants, see AirCondition.Com.

Model	Years	Engine Type	Factory Fill Refrigerant	Factory Fill, grams	R134 Conversion or R134a Refill, grams
760	82-87	B28/B280	R12	1200	1100
760	88-90	All	R12	1100	900
780	87	All	R12	1200	1100
780	88-91	All	R12	1100	1100
740	84-90	All	R12	1200	1100
740/940	91	All	R12	1100	950
960	91	B6304F	R12	1250	900
740/940	91-92	B230F	R12	1100	950
700/900	91	B204	R12	1000	900
700/900	92	B204/234/Diesel	R12	1050	950
700/900	92	Other	R12	950	900
900	93-	4-cyl	R134a	950	950
900	93-	6-cyl	R134a	950	950

[Symptom] After recharging my a/c system with R134, my compressor belt squeels and the clutch will only operate when I apply direct battery power to it.

[Duane Hoberg] You've overcharged your system. The high system pressures caused the compressor to lock up which caused the squeeling since the metal-to-metal clutch was slipping. Place a gauge on the low pressure test port and if above 40psi on the low side (R134), bleed some off and get the low side pressure to about 28psi.

[Tip from Larry Carley, Underhood Service, April 1999] In most instances and in most vehicles, a basic R134 retrofit procedure is all that's required to retrofit an air conditioning system. By basic, we mean recovering any residual R-12 that may still be in the system, draining out the old mineral oil, replacing the accumulator or receiver/dryer, and then evacuating the system to purge air and moisture, adding the specified amount of POE oil for the compressor and recharging the system to 85 to 90 percent of its original capacity with R-134a. It's important to remember that R-134a or any other alternative refrigerant cannot be mixed with R-12 or used to top off an R-12 system. If an A/C system still contains any R-12 at all, it must be removed using approved recovery equipment (venting is not allowed) before a new refrigerant is added to the system. This is an absolute must to prevent cross-contamination of refrigerants and cooling performance problems. R-134a and mineral oil won't mix. So if somebody recharges an R-12 system with R-134a and doesn't add a compatible lubricant, the compressor will soon fail.

Volvo was the first auto maker to approve POE oil (P/N 1161442-7) for R-134a retrofits. Volvo retrofit kits include a new receiver/dryer and O-rings (color coded yellow) for the expansion valve, and a new expansion valve or orifice tube. Volvo says the system should be evacuated for at least 50 minutes following recovery of the R-12 and component replacement to pull out as much residual R-12 as possible. Volvo also says the shaft seals on Sanden 508 and 510 compressors must be replaced when converting to R-134a. The new seal is P/N 9134344-2. If the compressor is being replaced, it should be filled with POE oil through the fill plug only, never through the inlet or outlet ports. Also, if the compressor is being replaced, Volvo says not to add oil to the receiver/dryer.

[Editor] At conversion, consider adding both a variable orifice tube and an in-line filter in the compressor suction line (both described below) to your system to improve low-end cooling and protect the compressor against any system debris.

Procedures: How to retrofit R134 into R12 systems.
Dave Urban developed a series of HTML pages showing the instructions and illustrations for the Volvo retrofit kit for 7xx cars, adding Dave's annotated comments from his own changeover. These files are duplicated, with thanks to Dave, here:

[Chris Herbst] There is only one way in my mind: using the Volvo kit. It is expensive compared with Wal-Mart's kit, but it is clearly one of the best kits I've seen for doing the job. All you have to get on top of the Volvo kit is the two compressor O-rings. There is no other way, there is no acceptable alternative, and there is no insta-conversion kit that allows you to bypass ANY ONE OF THE STEPS OUTLINED IN DAVE URBAN'S DESCRIPTION ABOVE. Skipping all or some of the above steps will result in a less-than-optimal conversion that may cause poor performance, system damage, or lack of proper function.

About a month ago, I retrofitted my wife's 88 765T to R134a, using the Volvo retrofit kit, which contains a new receiver-dryer, orifice tube, o-rings, and ester oil. I did it right. First, I had the system evacuated. Then, using compressed air, I blew out all the lines. Then I installed the new receiver-dryer and orifice tube, and then I pulled off the compressor (that was a job!) so I could empty the old oil out and add the new oil. Volvo gives you the oil for this, but doesn't tell you how you're supposed to change the oil without removing the compressor -- and apparently they don't expect you to, since they don't include o-rings for the hoses. What, do some Volvo compressors have a drain plug on the bottom? Mine has a fill plug on top, but no drain hole on the bottom. Anyway, I took it back to the shop, had them draw down a vacuum on the system, then recharge it with R134a (it takes LESS R134a, BTW). The result? 41 degrees F at the vent -- which is Volvo spec for the '88 765T. This was with the car sitting at the A/C shop, just idling, too.

[Tips Ex Post Facto.] My turn to share some info since I have just finished my part of the 134A conversion (vacuum/charge to be done at the shop next Tuesday. Here are my comments and advice:

[Tips from Lee Fox] RE: 740 AC conversion and variable orifice tube. I just got done converting my wife's 1990 740GL from R-12 to R-134a and thought I would report on the process. Many thanks to David Urban's most helpful web page describing the entire procedure. He gave me the encouragement to try it myself and he saved me at least $100. I purchased the conversion kit from Brentwood Volvo for about $50, but could not get one of the connections on the old accumulator off, so had to buy the supplemental kit for pre-1988 models for an additional $28. My system had leaked out all of the old R-12 from the original factory fill valve. The folks at the dealer said that this was common and now install the supplemental kit whenever they do the conversion. Following David's instructions, the changeover was easy, taking less than one hour. I rented an AC vacuum pump and gauges for about $25 and bought three cans of R134a plus some leak detector (I wanted to make sure I didn't have a leak elsewhere) and a charge hose for about $30 from Auto Zone. You have to evacuate the system for about an hour and it took about another hour to get it charged up. I had to jumper the low pressure switch to get the compressor going to suck in the first can. When I returned the vacuum pump I had to wipe to condensation from my glasses walking into the store - it was that cold inside the car! [Chris Herbst] Consider adjusting the R12-calibrated pressure switch on the receiver-dryer to cycle off around 20lbs. R12 is set higher.

[Larry Carley, Underhood Servide, April 1999, ed.] When a compressor fails, it can throw metallic debris into the system. Most of the junk ends up in the bottom of the condenser, but some of it can also be blown back into the suction hose. Flushing the condenser, hoses and evaporator with refrigerant or an approved solvent may remove most of the debris. One aftermarket supplier's A/C flush solvent, Dura 141, has seen successful acceptance by the repair industry. It has a boiling point below 90 degrees Fahrenheit, so leaving residual solvent doesn't appear to be a problem. However, modern parallel flow flat tube condensers cannot be flushed effectively because debris jams in the narrow tubes. Replacement is often recommended if debris is found in the system. Most experts also recommend installing an in-line filter (high side and/or low side) to protect the replacement compressor and orifice tube or expansion valve. [Editor:] Highly recommended: filter screens that can be installed in the suction line to prevent any debris from reentering the compressor (see AirSept, Inc. for such a product). Some Volvos may need to have this screen installed at the receiver-dryer because it will not fit at the compressor. Many compressor suppliers now require this to maintain warranties and avoid unwarranted comebacks.

If You Replace Any Hoses. Make sure you replace with R134-compatible barrier-type hoses

I would have to say that the person responsible for updating this particular 7xx system missed something. I have performed probably 25 of these conversions on 200 and 7/900 vehicles using the OEM kits provided by Volvo and all of them have worked as well or better than the R12. The secret is to use the proper amount of 134, if you overcharge or undercharge, the cooling output is diminished. In our shop we use the Snap-On charge station that charges the system by dialing in the amount digitally and forces it in by the kg or ounce. The only way to get the proper charge is to weigh the refrigerant before installation; no way you can guess and be accurate. The lack of cooling at idle could be from over/undercharged. Partially blocked condenser/radiator (bugs, dirt). Inoperative clutch fan or auxiliary fan. Too much oil in the system, wrong orifice tube (should be changed to a tan one), weak ac compressor, blocked accumulator or ac cycle switch set too high. The 200's are a different story but I have never had a complaint for insufficient cooling here in Georgia, even from a 245 owner. The new evaporator that comes in the Volvo kit is about 30% larger in surface area and the cooling capacity seems to be better than R12. Just for comparison purposes: Our shop gets $187.00 to convert an operating 12 system to 134 on a 7/900.(parts and labor) $375.00 for a 200. (parts and labor).

I recently did the same conversion on my 1989 745GL. I'm not terribly happy with the performance at idle either. After some experimenting I've decided there are a few things that can be done to improve things, none of which I have implemented yet...First thing is to make sure the fan clutch is in good working order. Second problem is if your mechanic put in TOO MUCH 134a! Problem is that the Volvo conversion kit only includes a low-side 134 filler port. There's no way to measure the high side using the new SAE 134 fittings. Because of this there's no way for the mechanic to know what's enough refrigerant in the system other than looking at the dials at fill time. The third thing that needs attention is the all too rudimentary aux cooling fan setup. In stock, on 7xx cars (excl 760 1988-), the cooling fan in front of the condenser is triggered by a temp sensor in the radiator. That's all well and good, but doesn't do squat about the condenser cooling. What's needed is the aux fan being ON whenever the compressor is on. A simple relay that lets either the engine coolant temp OR the compressor turn on the aux fan would be a good first line of defense. This would probably be sufficient for most apps in most parts of the world. BUT, this will also mean that the aux fan comes on when the system is put into DEFROST mode, as the A/C is always on then to dry the air.

If you're like me, you don't want that to happen when it's really cold outside. So that would require the addition of a temp cut-out switch to the above mentioned two-input relay. In addition, having the aux fan on at highway speed actually will DECREASE cooling performance because the fan is basically in the way. So add a speed sensor cut out to the above circuitry. Now you've basically got most of what the more modern 9x0 (1993-) cars have as standard. As a first test for you, skip all of this and try wiring things up so that the aux cooling fan comes on whenever the compressor comes on. You can fake this by connecting the two wires at the temp sensor up at the top right corner of the radiator (effectively bypassing the temp switch itself.) Use a paper clip or something, wrap it with tape, close the hood and drive around and see if this makes any difference. If this doesn't help I'm out of ideas.

If it does help somewhat (you'll obviously need some temp gauges to measure all this), there's always the option of grafting the 780 aux cooling fan onto your 740. Volvo has a kit for this, which I imagine is pretty pricey since it includes a brand new fan etc., but they needed it for markets such as Arizona, even BEFORE going to 134a! As far as I remember the kit doesn't include any of the logic suggested above, so I'm not sure it'll do anything unless some sort of A/C triggering is added as well. [Editor] See Recharge Tips above.

[Lee Fox] I wish I had heard about the variable orifice valve tubes before I converted. It sounds like a good idea. You can find out about them at http://www.aircondition.com/vov/ This is also a great site to learn all about automotive air conditioning. You can even take the test online to become EPA certified to buy R12. In summary, I would recommend the conversion to anyone who needs to fix an ailing AC. We be chillin'

[Chris Herbst] I've used several VOVs, and they are worth the money, the time, and opening the system to put them in. The VOV does not make a great difference on the highway, but in the city, under high transfer load, it does fantastic work. Sometimes it can lower vent temps five degrees plus. R134 is not the best refrigerant; the VOV makes the best use out of it. Also I believe that pressure-wise, it's better for the compressor since there is better oil transfer and the compressor system doesn't get backed up (too much heat to effectively transfer out between entering the condenser and exiting the condenser). Opening the A/C system is not a problem. In fact, it won't hurt to purge the system, add a little oil, recharge (and replace any or ALL available O-rings while you're at it) and enjoy better cooling especially in the worst conditions. If you are in a very hot climate (like Arizona or other areas where temps are routinely near 100 or more) get the VOV for high temperature environments. It has a slightly different operating range for best results in those conditions.

[Tips from A/C UPDATE: Retrofit Vs. Recharge, Retrofitting Techniques, Improving Cooling Performance & Alternative Refrigerants, Larry Carley, ImportCar, May 2000 (Excerpts)]:

One way to improve cooling performance when retrofitting an older R-12 system to R-134a is to install a variable valve orifice tube in place of the standard fixed orifice tube. These aftermarket variable orifice tubes allow the flow rate through the valve to change for better cooling at idle and low speeds. Such a valve can lower the A/C outlet air temperature by as much as 5 to 8 degrees, which can make quite a difference if the vehicle is crawling along in stop-and-go city traffic. Installing a larger or more efficient condenser can also help compensate for losses in cooling efficiency with R-134a. If the original condenser or evaporator is being replaced because of a leak, damage or defect, make sure the replacement unit has the same or better BTU rating. Some aftermarket replacement condensers and evaporators may not deliver the same cooling performance, and create a problem your customer didn't have before.

Location of Orifice Tube. [Chris Herbst] Later cars have the orifice tube installed in the expansion pipe. The joint at which to access the expansion valve is located along the right side frame rail in the engine compartment. It is where the high side pipe gets a little bit bigger in diameter. You'll find the OT in that joint. The earlier cars (with very small diameter pipes at the firewall) had it in the evaporator. The expansion tube location started in 1991, I believe, but that is not a guaranteed model year for the change. As a 1993 model, your car is sure to have the OT in the expansion tube.

[Editor] The R134 conversion debate seems to be over and it is widely accepted as an alternative to R12. Numerous other refrigerants are also approved by the EPA as having met safety and environmental criteria. Unfortunately, the EPA does not test these alternative refrigerants for compatibility with refrigerant oils, elastomers, and other components in your car's cooling system. Santech Industries, a major producer of air conditioning components, has done some tests and found R134 the only acceptable substitution product for most applications. See the link for more information in the "testing and reference" section: http://www.santech.com/

Volvo uses HNBR in its black and yellow o-rings (some earlier seals were blue neoprene). They also recommend the use of ester oil as the replacement lubricant in R12 to R134 conversions. After testing HNBR and ester oil, Santech rated the following fluids for compatibility with HNBR seals:

"Marginal" compatibility: FR-12 (Frig c: 59% R134a, 39% R124, 2% butane), RB-276 (Freezone:79% R134, 19% R142, 2% mineral oil)

Similar results came from the use of mineral oil instead of ester oil. "Poor" means seal swelling in excess of 40%; "marginal" between 16 and 40%. They note: "HNBR and Nitrile are used predominately in air conditioning systems worldwide and were not generally compatible with the alternate refrigerants." Some of the problems reported from material incompatibility include:

Conclusion: when you convert your Volvo from R12, use R134 and an ester oil. To improve performance, consider a variable orifice valve.

Condenser Replacement. [Inquiry] How do I replace the condenser after I have experienced a large system leak? [Response: Editor] To replace the condenser in a 90+:

If you had a leak leading to discharge in an R12 system, then convert to R134. Install the correct amount of oil per system specifications. In 1993+ cars, a new type of condenser and compressor pipe termination was used requiring different pipes that terminate in non-screwed ends. Make sure you buy replacement condensers that drop into your car without the need for new pipes.

Should I Flush or Install a Filter? [Tip from Underhood Service magazine, Apr 2003] Condensers are trash collectors. Any debris that comes out of the compressor goes straight into the condenser. It's a low spot in the system so debris and oil naturally collect in the condenser. But the debris doesn't stay put. Refrigerant flowing through the condenser can pick up debris and carry it to the orifice tube, expansion valve or back to the compressor. Debris can plug up the orifice tube or expansion valve, causing a blockage and loss of cooling. Such blockages also can prevent the circulation of oil in the system, starving the compressor for lubrication. If the condenser is dirty, why not just replace it? That's what many experts recommend. But condensers are expensive to replace. The alternative is to clean the condenser with an approved flushing chemical that hopefully will remove most or all of the contaminants. Flushing can save a customer a lot of money, but it also increases the risk of a repeat compressor failure or an orifice tube or expansion valve blockage if the flush fails to remove all of the gunk from the condenser. To reduce the risk of residual debris from a flushed condenser passing into the system and causing problems, an in-line filter should be installed in the liquid line after the condenser to trap any debris before it can cause trouble. A filter screen also should be installed in the suction hose at the compressor inlet to trap any junk before it can enter the compressor. Debris can be blown backward into the suction hose and evaporator by a compressor failure, too, so don't overlook this part of the system if you're flushing to get rid of contaminants.

740/940 Procedure. Read this entire section before commencing the job. The most difficult thing about this job is finding all the screws that need to be removed. Plan for a full day. Patience is vital, because if parts of the evaporator housing are damaged, you will have a very difficult time remounting the blower and obtaining a satisfactory seal. I paid $175 from fcpgroton for a new evaporator. The dealer will charge you about $1000-1200 to replace the evap and recharge the system.

Tips For Removing and Installing the Evaporator and Plenum Cover. [Jan Kinner] Taking an evaporator out of a Volvo 940 is not an easy job!! There is ZERO clearance to get to some of the screws that need to be removed (see illustration of MCC plenum unit in right side footwell). And even when all the bolts were taken off I still broke the evaporator drain spout pulling the thing out of the car. [Editor's Note: Broken drain spouts are quite common, so be VERY careful. ] The mating surfaces are filled with sticky mastic which must be pried apart. The evaporator, once disconnected from the a/c tubes on the engine side of the firewall, came out easily enough, but the new one was as stubborn as a mule. Note that the evaporator has two tubes that extend through seals in the firewall. We finally got it through the firewall and hooked back up, but that was the easy part. The tough part was putting the evaporator cover back on -- this took almost 6 hours to do. Tip: take out all the insulating material around the drain spout that goes through the fire wall. That will at least give you enough clearance to put the cover over the evaporator. Another suggestion... everytime you get a screw back in take a break. You are laying upside down in the car working over your head in the dark...very frustrating!!!

Tips for Removal of Lower Cover. [Adam Burke] It does not appear possible to remove that lower cover without breaking it unless you first remove the bolts that hold the HVAC box in place. The evap drain extension is in the way. When you have removed the screws and you are trying to figure out what else is holding the cover, it's wedged between that extension and the protruding evap drain. To get around this, remove two bolts at the fresh air intake and one on the firewall behind the receiver/drier. Instead of removing the exterior cowling and rain guard to get at the fresh air intake bolts, reach up through the fan shroud from below with a 10mm open/box-end combo wrench. Looking through the hole where the fan motor goes, the bolts are on the top of the metal bar, facing upwards. It's easy enough to do with the right tools and saves a LOT of time. The bottom evaporator cover comes out much easier front-end (firewall end) first. It's counter-intuitive, but there is more room to pull the drip tube clear of the firewall drain hole this way. The wrong way: If you pull the back of the box down first, the front part pivots against the bottom of the evaporator and pushes the drip tube forward against the firewall -- not what you want. Worse, this puts a load on the drip-tube area of the box, and it's likely to break at this point. (You can't see what's going on while the lid is in place, so you can't actually see the cover wedging against the evaporator.)

Tips for Installation of Lower Cover. But - if you've loosened the bolts and air intake mount that anchor the HVAC box, it probably will have dropped some. If it has dropped even 1/4", the lower cover won't fit at all: It will run into the firewall before the screw holes line up. If I had to do this again, I would first see if it would help to have an assistant push up on the evaporator while I remove (and later replace) the lower cover, although this will be difficult because you both need to be in the same place at the same time. . If that wouldn't work, then I would remove the HVAC box mounts and pull the whole thing away from the firewall as much as it could go before I would work on the lower cover. A wedge - such as a rag stuffed behind the box - might help hold it out temporarily but frankly it didn't work for me. When reinstalling if you don't have a helper, use a ratcheting strap (those flat, nylon straps with ratcheting tighteners you can get almost anywhere) wrapped around the HVAC box just to the left of the evap and anchored around the pillar between the front and rear doors. It doesn't take a lot of force, but it helps to have something holding the box away from the firewall. You also need to have the box pushed up while being held out, so place a small hydraulic bottle jack and a large, flat piece of wood under the box (about in the same location as the strap). Again, it's not force that is needed; just something that will sit there and patiently hold the box for you. To re-install the evaporator cover, put the rear in place first, then swing the front of the cover upwards. You'll still have to wrestle with the whole thing to get the drip tube back up into the firewall, but it won't be nearly as difficult as trying to put the cover on front-end first. [Gary Hammett] When reinstalling the cover, make sure you align the passenger side flange at the firewall (inside), or you never get the cover pushed back. There is a flange or rib on that side. Rotate the cover into that flange first and then worry about the driver's side. The small bulge in the cover for the evaporator pipe at the rear of the cover is just large enough for you to use the sole of your shoe to help push it into place. After I did that with a bit of working the cover back and forth at the front, it popped into place. Don't use a rubber mallet to fit the cover or you'll crack it and have to repair it.

Cracks in the Lower Cover. [Adam Burke] I don't know of any way to repair this kind of plastic. It doesn't respond to the plastic primers and glues that I normally use. If you sand it, JB Weld epoxy will adhere, but JB Weld won't give you the strength the plastic had before it cracked. I also tried to patch it from both sides with fiberglass, but the fiberglass wouldn't stick - even to the sanded surface.

[Editor] Your evaporator is far easier to remove than that in a 740 or 940. Remove the battery negative and evacuate the air conditioning system. Remove the firewall connections, including the metal plate and washer, for the pipes leading to the evaporator. Remove the glove box and passenger kickpanel, then the plastic evaporator cover. Pull the evaporator out. You may have to remove the air bag bolster (the large metal bar near the glove box) if it is in the way of the evaporator.

Hose Replacement. [Tip from Rafael Riverol] When I retrofitted my 760T A/C from R12 to R134, I put in all new Volvo parts from Swedish Engineering including new hoses. Soon, I found the entire hose from the compressor to condenser glowing green with UV dye because R134 was leaking right through the body of the hose. Later, I found out that Volvo has information out recommending use of barrier type hoses when retrofitting A/C to R134. It turns out, original hoses will hold R134 only when saturated with mineral oil used with R12. New hoses or flushed out old hoses (cleaned of mineral oil) will not hold R134 because its molecules are smaller than those of R12. I had received and put in the car an original Volvo hose good only for R12. Be sure to put in new barrier type hoses designed to hold R134 when retrofiting from R12. Rebuilding Hoses. I've found that flexible ac lines typically start leaking at around 100k miles and can be expensive to replace. I've located a repair service in Tucson that can fix your existing line for around $50: mail them the old hose and they rebuild it . They seem to do good work. Century Auto Air.

General Notes. [by Larry Carley, Import Car Magazine] The most common symptom of a compressor failure (besides no cooling) is a seized compressor. It won't turn when the magnetic clutch engages, and you may hear squeals of protest from the drive belt. Or, the belt may have already broken or been thrown off its pulleys. Loss of lubrication is unquestionably the most common cause of compressor failure. This can happen when there's a refrigerant leak somewhere in the system that allows refrigerant and oil to escape. Typical leak points are hoses, hose and pipe connections (O-rings and flange gaskets), the evaporator, condenser or the compressor shaft seal. An electronic leak detector or dye should be used to find the leak so it can be repaired. A restriction inside the A/C system can also starve the compressor for oil. Oil circulates with the refrigerant, so if the orifice tube or expansion valve is blocked it may cause the compressor to run dry and seize. Even if a compressor is still turning, it may have to be replaced if it's leaking, making excessive noise or not working correctly. Some compressors are naturally noisier than others, but loud knocking noises can sometimes be caused by air in the system (the cure here is to vacuum purge the system to remove the unwanted air, then to recharge the system with refrigerant). Metallic noises and bearing noise are usually signals that the compressor is about to fail. A new compressor may be needed if the unit is leaking internally or not producing enough pressure due to bad reed valves, worn piston rings, or worn or scored cylinders, etc.). A worn compressor or one with internal problems will not be able to develop normal operating pressures with a full charge of refrigerant. This kind of problem can be diagnosed with an A/C gauge set. Poor cooling can also be caused by a lot of things other than a bad compressor, so don't replace the compressor until you've ruled out other possibilities such as a low refrigerant charge, too much oil in the system, air contamination, a clogged condenser, plugged orifice tube, inoperative electric cooling fan, etc.

General Notes. [by Larry Carley, Import Car Magazine, May 03] If the compressor isn't turning, make sure the magnetic clutch engages when energized. Underlying problems here may include a bad relay, fuse, wiring problem or a defective clutch. If the clutch fails to cycle on and off when the A/C is turned on, jumping the clutch lead with a jumper wire from the battery will show if the problem is in the clutch or elsewhere. If the clutch engages, the problem is the clutch power supply (relay, fuse, wiring, switch or control module). Refer to a wiring diagram and work backward toward the battery to find out why the voltage isn't getting through. Many A/C systems have a low-pressure cutout switch that prevents the compressor clutch from engaging if system pressure (the refrigerant charge) is too low. This is designed to protect the compressor from damage in the event of a leak. So if the clutch isn't engaging, check the refrigerant charge and the cutout switch.

Diagnostic Notes. [Diagnostics] Where can I hook up a jumper wire to see if the AC compressor clutch is still good?

[Herb Goltz] In 740 cars, remove the connector at the low pressure switch on the accumulator/dryer (the aluminum cylinder at the firewall). Jumper across the two terminals inside the connector (a paperclip works fine). With the AC set to on and the engine running, the compressor should engage IF the terminal inside the connector is receiving +12V power via the 10-second delay relay behind the glove box. In 940 cars, remove the same low-pressure switch connector at the receiver-dryer and jumper it: current comes directly from terminal 10 of the MCC control unit with no relay.

[Larry Spooner] If there is a circuit problem after the above test and you want to test the compressor directly, unplug the connector in the black wire going into the clutch assy. If you have an ohm meter there should be a low resistance 3-5 ohms measured at the compressor side of the connector to the compressor body or engine block. You should be able to jumper this directly to the pos battery terminal or the B+ terminal on the back of the alternator and see the clutch activate. The engine does not have to be running. Because of the low resistance of the clutch coil there's going to be a little bit of a spark.

[Symptom:] My '86 760T is losing its compressor clutch. What does it take to change this clutch?

Apparent Clutch Failure Caused by HVAC Control Unit. [Jim Holst] My '93 945 AC compressor would not come on but I measured nearly 12 v from compressor lead to ground. I was puzzled that the compressor was not engaging. Eventually I pulled the control unit out of the dash and inspected the printed circuit. As noted below, the solder connections at the small,black relay box were cracked. I resoldered the relay connections and the AC now works fine. What was happening was this: the cracked solder joint made a high resistance connection. This allowed enough current to flow to let the voltmeter read nearly full battery voltage. When the compressor tried to run, the high resistance, cracked, solder joint would not let enough current through to energize the compressor clutch. If you know Ohm's Law, think of a series circuit with the 3.4 ohm clutch in series with something like a resistance at the crack of 100Kohm. A 10 megohm input meter would read nearly the full supply voltage but not nearly enough current would flow to operate the clutch. There is a way to test this without pulling the control unit. If you connect your voltmeter to the compressor connection from the rear of the connector without disconnecting the compressor, you can measure the voltage when the compressor tries to engage. If the solder connection is cracked, the voltage will drop to nearly zero. With the connector open, the voltage will be nearly 12v.

960 Sanden Clutch Failure. [Tip from Ross Gunn] My '95 960 clutch disintegrated due to heat damage to the bearings. The compressor is a Sanden SD7H15. I suspect the order of events was: 2 out of 3 clutch springs broke, clutch started to slip causing great amounts of heat, bearing lubricant dried/burned, plastic bearing cage melted, bearings became unevenly distributed around the race, clutch contacted windings of coil. I searched far and wide for a new clutch. The only source I could find was Volvo (over $350 Canadian - $225US). I ended up having the compressor replaced at a non-Volvo A/C shop. They used a different model Sanden compressor, but the system seems fine now.. 3 1/4-20 (IIRC) screws to pull the pulley, I don't know what the spec is.

Clutch Bearing Replacement. [Robert Reagan] If you have noise coming from the A/C compressor bearing you can replace the clutch and/or bearing without removing the compressor. I was hoping to avoid having to open the system to remove the compressor and then having to replace the receiver dryer and recharge the R134a. The tricky parts of the job were maneuvering the circlip tool around the shaft of the compressor using a mirror to see to remove the circlip holding the pulley on, plus pulling the clutch off the shaft without a proper pulling tool. But it can be done. A local bearing supply house was able to match the bearing with a duplicate - it even had the same number stamped on it. I pressed the bearing into the clutch with the help of a little oil on the outer bearing surface. Put the clutch back on the compressor, installed the circlips and nut, and was off to the races. Engine is much quieter now that there is no bearing noise, and I don't have to worry about a seized bearing interrupting any trips. The entire repair cost $20.

Clutch Removal [Tips from Loren Rux/Ross Gunn] Remove the radiator for better access. There are three threaded holes for 5mm bolts in the clutch plate, and I just assumed they were for removing the clutch plate by evenly screwing in three bolts, forcing the plate off the shaft. Whether or not that is the purpose of the threaded holes, it worked. After the plate was about ½ inch out, it came easily. Then remove circlips/snap rings to get the bearing and coil off. There are also some shims that adjust the clutch gap; it is important to get these right on reassembly.

[Tip from David Steffy] If you don't want to open the A/C system, you can replace just the clutch & bearing ass'y. (It's possible to get just the bearing, but not to replace it in the clutch.) Got mine at the local import auto parts store for ~$125. You'll need a puller tool to get the clutch off. The K-D one for GMs works, and can be borrowed or rented at some auto parts stores. Note, this is not an ordinary 3-arm type puller. Otherwise the swap is straightforward and leaves you with a new clutch plate as well.

[Another Response:] There is a special tool (naturally) but it just pushes it off by attaching to the threaded fitting in the hub of the face of the clutch. Once that is off, there is a snap ring at the front which holds the pulley and bearing on. Tapping on the pulley will slowly move the assembly off the front of the compressor. Then there are 3 Phillips head screws which hold the coil on to the front of the compressor. These round off easily so try tapping on them with a 3/8" #2 phillips bit before trying to turn them.

Clutch Sources. [Tip from Rafael Riverol] Clutches alone may be had from www.hancockindustries.com. Most suppliers sell only the complete compressor with a clutch.

Diesel Kiki Models. [Inquiry] My '87 700 has a Diesel Kiki a/c compressor that has seized. Is it rebuildable (by me?) or smarter to just remove & replace? Are rebuilts available? Are they good as new? [Response: Tom Irwin] In the years I worked in aftermarket I probably bought between 50,000 and 100,000 Diesel Kiki's, as rebuildable cores. What can I tell you... Well, in general they are CHEAPLY built and not very reliable compared to Nippon-Denso, Panasonic, etc. Is it rebuildable (by me?) No. Are rebuilts available? TONS! EVERYWHERE! Are they good as new? Sometimes they are better...the aftermarket KNOWS which components fail and endeavor to improve the unit. Look for who manufactured it... Murray/Moog, Four Seasons, AC Plus, are all EXCELLENT rebuilds. ASK the parts guy who makes their private label stuff Can the clutch be replaced without discharging the system? Yes. One last note... Diesel Kiki's, that were converted to 134a are shit. Since you are going whole hog... get a 134a pump...new receiver/drier... do it right. 12 is just too much hassle. [Response: Lamar] You can get a new one for just over $200 at Autozone or Advance. They come ready to use either R-12 or R-134a. I just replaced one on an 88 740.

Sanden Models. See the Sanden Corporation website, under Support, for a full service manual and parts information for their compressors.

Volvo 7XX/9XX Air Conditioning Compressor Lube Capacity Chart
Note: OEM lube oils for R134 OEM systems come in several PAG viscosities depending on compressor: one for Sanden SD-7H15 (Volvo p/n 1161425-2); one for Seiko-Seiki SS-121DS5 (Volvo p/n 1161426-0); and one for Diesel Kiki/Zexel (Volvo p/n 1161407). They may not be intermixed.		Lubricating Oil
Note: R134 retrofit oils are always ester: Volvo p/n 1161442-7		R12: Mineral Oil
		R134 Retrofit: Ester Oil
		R134 OEM Install: PAG Oil
Compressor:	Model:	Metric (L)	English (Qts)
Delco	R4	0.30	0.32
Diesel Kiki	DKS-15BH	0.20	0.21
Sankyo Sanden	SD-510	0.24	0.25
	SD-709	0.24	0.25
	SD-7H15	0.24	0.25
York	210	0.30	0.32
Zexel	DKS-15BH	0.20	0.21
	DKS-15CH	0.20	0.21
Seiko Seiki	SS121 DS5	0.22	0.23

If you remove any components of the air conditioning system, you need to add back the amount of oil usually found in that component using one of the oils shown above. Here is a guide:

Compressor (same as amount removed from old compressor OR 75cc/2.4 oz. minimum)
Condensor 22cc/0.7 oz.
Evaporator 53cc/1.7 oz.
Accumulator/Dryer 95cc/3.0 oz.
Lines 22cc/ 0.7 oz

Mold Odor from A/C System. [Tip from Editor] I have had a similar problem on both my 1990 745 and 1995 944: mildew-like odors from the air conditioning system, especially when starting the car again after it has been sitting for some time in the heat and humidity. To prevent it, limit your use of the recirculation function and turn the a/c selector to vent about three blocks before you reach each destination, allowing the evaporator to dry out before shutdown. Before you proceed, try cleaning out the evaporator drain so that debris does not cause the problem to recur.