Heating and Air Conditioning                                                                          FAQ Home
Volvo Maintenance FAQ for 7xx/9xx/90 Cars                                                                                                                     Version 5.0
Heater Vacuum Controls

Access to Heater Control

Air Conditioning Vents Not Working

960 A/C Vent Stops Working Upon Acceleration

Squeaking Blower Motor

Heater Blower Motor Replacement

1992 700 Blower Motor Only Runs "High"

Replacement Blower Motors for 7XX pre-1990

Leaks in Ventilation System at Blower Motor

Poor A/C Performance: Diagnosis

Air conditioning: R134 change from R12 in Volvo cars

R12 versus Refrigerant Alternatives

A/C Compressor Failure: Electrical Ground

Compressor Clutch Failing

Removing the AC Clutch on an '89 760

Rebuild or Replace Diesel Kiki A/C Compressor?

A/C Hints in Hot Weather in Post-92 Models

Mold Odor from A/C System

Interior Water Leaks: Clogged Evaporator Drain

Heater Not Working

Heater Core Leaking

MCC Climate Control A/C Not Working

ACC Heater Control Not Working

ACC Climate Control Instability

ACC Air Conditioning Sensor Not Operating

ECC Climate Unit Diagnostic Codes

Replacing Vacuum Servos in ACC-Equipped 700/900 Cars

Heater Vacuum Controls. [Symptom: leak sound from heater controls.] 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.

Access to Heater Control: Remove the glove box and you can see in there if the warm/cold air flap arm is moving as you move the lever. If you need to go further, to best get access to the rear of the HVAC controls, remove the complete ashtray assembly (as if replacing a fuse), remove the plastic compartment above the ashtray (two screws behind the plastic cover surrounding the cig lighter) and then PULL out the radio from the plastic box it lives in and undo the Phillips screw at the back of the radio box and pull it out. Then remove the plastic panel around the HVAC controls (just pull on it, it's not that brittle), and you will expose a few Phillips screws that hold the HVAC controls in place. Unscrew and pull out the entire mechanism, which is pretty hard since there's hardly any slack in the wires etc.

Air Conditioning Vents Not Working.  [Query; 86 740:] Every now and then, when using just vent or a/c, the air stops coming out of the panels vents. If I switch to defrost, I can feel the air, so the fan is  working.  [Response:]  There are 4 areas where the source vacuum can be shut down and make your vents not change over:
1. [From Bob]  Start by checking the vacuum supply hose under the hood. Under-dash leaks are extremely rare. The vacuum hose for the A/C-heater can be found under the intake near the trans dipstick tube. Look for a small (1/8" diameter) white plastic hose. It goes from firewall near heater hoses and winds its way to a tee with a check valve conected to a larger hose, ending at the intake. It is common for the hose to rub through from chafing on other hoses or wiring harnesses. When you find the leak, cut the hose and splice with a small piece of rubber vacuum hose.
2. the hose into car near accelerator pedal under hood has no vacuum on it due to being disconnected or damaged
3. inside the car under dash that same hose can be crushed up above and to the right of accel. pedal. Repair it with a piece of the rigid little spray tube that comes on aerosol cans like WD-40
4. behind the control head there is another place where there is a "y" fitting in the source vacuum hose that can collapse. Repair as in #2
5. The floor/defrost diaphragm is leaking. This is on the driver's side end of heater case above and to the right of accel pedal and it is the yellow hose. Plug it up with something and see if it returns to working, if so then leave it plugged as the cost of repair is high and the compromise in function is minor unless you live in a really cold place (floor air volume will be lower).
6. the vacuum canister behind the front bumper has a vacuum leak. (usually the rubber nipple on the end is split)
These were listed in the order that I suggest to check but Murphy's laws will likely make the solution be at the opposite end of list from which you choose to attack.

960 or ACC Vent Stops Working Upon Acceleration.

General Notes.  [Query:] My friend has a '94 960 and the air stops blowing from the vents while the car is accelerating (the a/c fan is still spinning but no air is coming out) when ever the car reaches a steady speed it starts blowing again. The same thing happened to me in an '90 760t and it turned out to be a hole in the vacuum line that goes to the vacuum reservoir. However I can't locate the reservoir in this car. Does anyone have any ideas?  [Response: Rich Kelley] The problem you describe sounds like one I've seen quite a bit on 960's. It sounds like a ruptured diaphragm on the flapper control solenoid. There is an illustrated, detailed repair procedure at Replacing Vacuum Servos in ACC-Equipped 700/900 Cars.   It's located on the drivers side. Take down the knee bolster and look up on the side of the climate control box. There are two vacuum controlled solenoids there and the one that usually goes is the one with 2 hoses going to it. It is very hard to get out, as it is held in place by 2, 10mm nuts on the inside of the box.

Look Under the Hood First.  [Tip from Bob]  Start by checking the vacuum supply hose under the hood. Under-dash leaks are extremely rare. The vacuum hose for the A/C-heater can be found under the intake near the trans dipstick tube. Look for a small (1/8" diameter) white plastic hose. It goes from firewall near heater hoses and winds its way to a tee with a check valve conected to a larger hose, ending at the intake. It is common for the hose to rub through from chafing on other hoses or wiring harnesses. When you find the leak, cut the hose and splice with a small piece of rubber vacuum hose.

Try Cleaning It.  [Tip from Larry Jacobson] Before doing any cutting and sawing, your arm up into the air intake that goes up in back of the glove box. You may be able to feel bits of plastic or paper or other light foreign matter that has been sucked into the system and is causing the flappers to not close. The vacuum motors huff and puff and hiss trying to slam the doors on the accumulated crud. I've had to do this twice and both times found all sorts of stuff up in there.  My wife has a habit of clipping coupons in the car. Bits of paper fall to the footwell and some get sucked into the AC system. Makes a racket like baseball cards in the spokes of the old Schwinn bike.

Replacing the Vacuum Motor.  [Query:] My heat/ac won't come out my vents, it will come out the defrost and the floor vents, but not my  regular vents.  [Response: Dick Riess] The vacuum motors are located on the drivers side. You need to take down the portion under the dash and kick panel against the radio area. These are not easily replaced (if that is what is wrong), but through a shortcut suggested by Tom Irwin and receiving some of my mods, I have done one on my 91 940SE. It is kind of the Don Foster approach, in his case replacing the heater motor on 240s.  There are 3 motors and fortunately the most accessible is generally the culprit and has two hose connections. First try a Mighty Vac and hook up a tube to each of the connections and see if they hold a vac. If one doesn't, you have a bad vacuum motor. Have to disconnect the hoses on the motor first, of course.  Do your diagnostics first.
[Response: Abe Crombie] To expand on what Dick posted:  The likely culprit, assuming the vacuum supply is coming in from the engine compartment, is the floor/defrost servo. It is a double acting (no vac centered= floor/defrost split, vac on blue hose = defrost, vac on yellow hose = floor) and has a boot on the floor side that retains vac on that side of diaphragm. The boot fails and you lose vac. Blocking yellow hose fixes it simply with compromised floor air volume (floor would be floor/defrost). All of this aforementioned stuff is usually the case if symptom is loss on acceleration.
You don't mention whether it is a 740 or 760. The 760 has an electric vacuum valve set to left behind glove box and a cold soldered joint on it at one of the end pins will cause no response in any position which defaults to floor/defrost. The 740 is a rotary vacuum switch linked to slide lever for vent selection and the hoses behind panel (white is source) can be crushed or the feed hose (white) above accelerator pedal at firewall can be crushed.
[Response: Abe Crombie, regarding 1990 760T with ECC: air stops coming out of any vents during turbo boost (manifold pressure instead of vacuum), indicating a leaky push-pull vacuum servo)]  The Floor/Defrost servo you discovered leaking is sprung to return to center when no vac is applied. This will direct air reaching this part of the air distribution housing to the defrost and to the floor outlets. The yellow hose applies vacuum to the side of diaphragm that will extend the servo rod to push the door up blocking most of the defrost vent air and directing 90% +/- to floor. The seal that rides the servo rod can dislodge or just split and you have the result you observed. Disconnecting the yellow hose will not allow you to get full floor air. When the floor air position is selected (by you or by the ECC logic) the air will be split between floor and defrost. This is likely not a problem unless you have really poor leg circulation that gives you a severe tendency to cold feet long after the rest of your body is warm. The logic in the ECC always has the floor position selected on this servo when it is directing air to the dash face vents so if it leaks you lose the vac for entire system and all the doors go their respective sprung positions.

Squeaking Blower Motor.  [Query:]  How do I fix a squeaking blower motor?  [Response]  Try removing the motor and oiling the bearings, if they are accessible in your model motor.  [Response 2: 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. Just remove the trim and panels around the floor, and remove the ECM from its mount. The ECM bracket is them easily unscrewed for removal. The blower is just above and easily replaced with 3 screws. I had to rewire the connector with a soldering iron, but that was no big deal.

My '88 745T had not had its motor replaced, so I had to do the mod. Just do the above procedure and follow the direction for the mod that came with the motor. Needed 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 mounted the new motor, solder the wires, and close everything up.

In both cases, the squealing went away and life quieted down a lot. One observation I made was that the cage on the new blowers are not as deep as the OEM blowers. Hence, the cage will not come as close to the air input port of the duct work. This may cause less efficiently in moving air to the cabin of the car. i.e., less air moving through the vents. Despite what I think is less air flow, I still get plenty of heat and AC. At least the squealing is gone, so I can't complain.

Heater Blower Motor Replacement.  [Query:]    [Response 1:  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 5 screws holding the blower motor in place and remove the blower motor.   Remove the ground wire from the old motor and unplug the power wire. Install new motor in reverse order. Some cutting and modification may be required depending on the style of the motor. I have done several of these, always in less than 1 Hr. [Response 2: 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.

1992 700 Blower Motor Only Runs "High".  [Query] 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 for 7XX pre-1990. [Note: Latest comment: There is no GM part equivalent to the Volvo blower motor for 1990 and later 7xx/9xx. The part may work fine in an earlier Volvo. The Volvo replacement part has been redesigned from the original 1990 part so you can't just get the blower motor assembly - you need the assembly, a new plastic mounting plate, and according to parts person, a new resistor added to the switch.]

[First comment: GM mid-80's blower motors for AC Chevy Citations are exact replacements. Also: look for an '81 Delta 88 w/ air conditioning blower motor. Also: The replacement for the 760 series fan motor is a standard GM fan motor. The NAPA part number is 455-1076. Also: 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.]

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.

Leaks in Ventilation System at Blower Motor.  [Query:] The blower motor in my 700 has been changed (for the cheaper GM unit) and has filled up with water from somewhere twice. Any thoughts as to where this is coming from or how to prevent it from filling up with water?  [Response:]  I had a similar problem; under the cowling (just forward of the windshield, aft of the hood) there is a black plastic shroud that covers the air intake (actually it's just the top of the motor housing) to the blower motor.  In my brick, the plastic had detached from the windshield edge and hung down, allowing water to pour directly into the blower.  One of the few bad designs on the 7xx brick, IMHO.
[Editor's Note:]  Check that the blower motor mount in the air plenum is not cracked.

Poor A/C Performance: Diagnosis.  [Query:] 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.

[Query]  Need help with my '91 740 Turbo Wagon A/C system. It works great when Im 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]   YES, your electric fan is supposed to be on AT ALL TIMES when the AC is running. My guess is if you pull your grille out, and reach in there, 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.

Air conditioning: R134 change from R12 in Volvo cars.

Basics on Air Conditioning R134 Retrofit.  [Tip from Larry Carley, Underhood Service, April 1999]
In most instances and in most vehicles, a "basic" R134 retrofit procedure is all thatís 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.

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.  The following kits are available from Volvo:

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.
    [How to retrofit R134 into R12 systems:] Great website from Dave Urban showing the instructions and illustrations for the Volvo retrofit kit for 7xx cars and Dave's annotated comments from his own changeover: http://www.prismnet.com/~davurban/AC_RETROFIT/Page_1.html
    [More how-to:] 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.
    [Lack of adequate cooling after retrofit:] 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.   [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:

R12 versus Refrigerant Alternatives: General Opinions. There is a lot of misinformation (and intentional disinformation) flushing through the car hobby and repair industry about the state of auto A/C in 1997. We see people rushing to convert their perfectly good R12 systems to R134a, we see people demanding R134a systems for new installations, and we see charlatans pushing ineffective, dangerous, and/or non-approved refrigerants and repair techniques. Worse yet, we see even bigger charlatans claiming that R134a is almost magical in its ability to go into any system, cool as well as R12, never create any compatibility problems, insulate your house, filter your coffee, and get your clothes whiter, brighter, longer. (Well, okay, maybe not those last three, but you get the point. R134a is being passed off as some kind of magic bullet for A/C systems.) The fact is that 134a, while it is nearly universally used in North America and many other countries as the OE refrigerant in '93 and newer cars, has numerous significant disadvantages over other refrigerants.

[Another Comment:] It is not a good idea to convert your R12 car to R134a or any of the R134a-based refrigerants (FRIGC and Freeze-12 come to mind). They are, relatively speaking, extremely inefficient refrigerants. Also, they are HIGHLY incompatible with R12-type oil. They operate at radically different pressures, so calibration of R12 expansion valves won't be optimal. Also, since 134a is so inefficient, one must use larger compressors, condensers, and evaporators to get the same level of cooling as from an R12 system. This is difficult and expensive to do on an existing system, so you get much less cooling with 134a. Perhaps most troubling is that R134a, unlike most other refrigerants, is not chemically inert. It is reactive, and has been shown to cause reproductive damage and is a suspected carcinogen.

Now that I have detailed some of the disadvantages of converting, let me outline what you would need to do to convert to 134a so as not to shell any of the components [Editor's note: see above remarks for Volvo-specific information and retrofit kits.] You're going to need:

In addition, you're going to want to purchase a new condenser of the "manifold" or "parallel-flow" design to try to get as much condensing surface as possible for the refrigerant. The inefficient 134a, under high-demand situations, must literally be *forced* to condense. The serpentine condensers used in R12 systems do not have this capability.

People often cite low cost of the R134a refrigerant itself as a reason for converting. Have a look at that list above and it becomes readily apparent that $80 worth of R12 vs. $20 worth of R134a is an irrelevant comparison.

There are other legal, safe, effective and efficient options if you have decided, for whatever which reason, to convert your system to a non-12 refrigerant (more on this later). Various companies have brought various refrigerants to market. Many of them have been minimally tested, have disadvantages similar to 134a, and/or other deployment difficulties. For instance, a lot of the new refrigerants have a very difficult time carrying any kind of oil back to the compressor. R12 has very good oil carrying capability, so the vast majority of existing compressor designs are meant for use with a refrigerant that will bring the oil back and lubricate the compressor. New oils have been developed to work reasonably well with the new refrigerants, but industry data confirm that compressor failure rates are up since the advent of refrigerants that don't carry oil as readily.

My own research and testing has turned up two very interesting refrigerants that seem to work extremely well, with minimal deployment difficulties. Those are R406a, and GHG-X4. Both refrigerants were invented by a Professor George Goble of Perdue University in Indiana. I don't work for the company, I don't sell the stuff, I have no association with Mr. Goble or anyone else on his refrigerant staff, except I've communicated with them by e-mail a few times. I point this out to indicate that I'm not trying to sell something, don't have any particular agenda or ulterior motive, etc.

Here is a rundown of some of the advantages of these two products as conversion refrigerants (actually, EPA's preferred term is "substitute" or "replacement" refrigerants.)

 Are there any disadvantages? Yes, and here they are: Now I have to ask YOU a question: Why are you converting to anything or demanding a non-12 refrigerant? R12 is still around, you know, and anyone who tells you otherwise is lying or ill-informed. There is plenty of it in the US. There is MORE than plenty of it in the US. And there will be for a very long time. The best policy if you've a working R12 system is to keep it an R12 system.

Some will tell you that R134a is the only legal refrigerant. That's wrong. Go to the EPA SNAP (Significant New <refrigerant> Alternatives Plan) homepage and see for yourself that many new refrigerants, including 406a and GHG-X4 have passed all the safety tests, are certified nonflammable/non-corrosive, etc.

Some will tell you that 134a "moves more heat" than R12. That's also wrong. Some will tell you that no flush, rebuild, or anything else is needed when converting to 134a, and that you can just drop 134a into an existing system. For most systems, That's dangerously wrong.

Information on conversions and refrigerant alternatives can be found at:


A/C Compressor Failure: Electrical Ground.  [Tip from Bob Simon] Last week I posted a problem with my A/C abruptly stopping. I had checked the fuse, but had not looked closely enough at the wires leading to the compressor.  Turns out that the ground wire for the compressor was corroded and the connection failed. A new connector was crimped on and re fastened to the compressor and it seems all is well now.  Go figure. At least it wasn't a clutch or solenoid.

Compressor Clutch Failing. [Symptom:] My '86 760T is losing it's compressor clutch. What does it take to change this clutch? [Diagnosis:] First is it really the clutch?1) If the compressor is starting to seize internally that will cause the clutch to slip and burn but the fix is a new compressor. 2) Is it the pulley bearing making noise? That requires a special tool to hold the front plate while you unscrew the big nut on the input shaft. The clutch and pulley then press off. You need to remove the freon since you're working at the front seal. 3) If the clutch is really worn out get the special tool and press it off. You can get another at a u-pull-it yard. However compressor rebuilts are not that expensive and really once you're at a u-pull-it yard the cost of a clutch vs a compressor is about the same. So I'd say replace compressor, either used or rebuilt.
Clutch Removal  [Tip from Loren Rux]  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.

Removing the AC Clutch on an '89 760  [Query:]  The compressor turns by hand OK but the clutch is burnt white and occasionally screeches.  I have the belt off and the center bolt out
but cannot get the pulley to move.  Gentle prying has not moved it. Any suggestions?
[Response:]  Keep prying. 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.

Rebuild or Replace Diesel Kiki A/C Compressor?  [Query] 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 to 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.

A/C Hints in Hot Weather in Post-92 Models. 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:
 1. refrigerant level is getting low. The un-boiled refrigerant on a full system that returns to compressor will cool it. If it's low this doesn't occur and off it goes.
 2. If it's over 100 F outside the a/c shutdown will occur due to compressor getting too hot. You can prevent this manually selecting recirc when it's this hot as the re-circulated air entering evaporator will allow the return refrigerant back to compressor to cool it down enough to prevent this. Don't let it stay on recirc forever as this will lead to a much increased likelihood of a/c odors. Turn it off recirc at night or when the temp gets back to normal (if it ever does in TX)

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.
You have two effective means of fixing the odor problem once it starts:
a. [For a mild case of mildew; evaporator and plenum don't have accumulated leaves, etc.] Buy a spray can of BG Frigi-Fresh. This is an evaporator disinfectant made just for a/c systems by BG, the same people who make BG44K. Contact BG for a local distributor (http://www.bgprod.com/).  A small can, sufficient for many treatments, costs approximately $8. Remove the passenger kickpanel under the glovebox and the right side kickpanel covering the computer module. You will now be able to see the air plenum and the blower motor. Near the blower motor is the blower resistor with wires going into it. Using a 1/4 inch drill, carefully drill a hole in the plastic plenum about one inch to the bottom-left of the resistor, sufficient to allow you to maneuver the spray tube of the can so as to spray toward the driver-side of the plenum. Approximately two inches to the left of the hole is the evaporator core, which is around 8 inches wide and 8 inches tall, oriented on the long axis of the car. (If you want to inspect the system, remove the glove box and  blower resistor.) Turn on the engine, engage the a/c system with the blower on "3". Spray a generous dose of FF through the drilled hole all over the evaporator core. Turn off the engine and let the treatment dry. Cover the hole with duct tape and re-assemble the kickwell. You will have a disinfectant odor for about a week, and the treatment should last a good part of the season. The hole will make it easy to reapply the FF next time. The whole job should take about an hour.
b. [For a worse case of mildew, along with accumulated crud in the system.] Same disassembly procedure as above, only remove the blower motor and lower plenum assembly as a unit.. This requires removing the glove box and engine computer to secure good access,  then the motor and resistor wires, then around eight screws holding the lower plenum on. Using a shop vac, remove accumulated crud (leaves, dust, etc.) and swab out the plenum with disinfectant. Clean the foam filter on the downwind side of the evap core.  Either use a treatment of Frigi-fresh on the evaporator as above, or go the whole nine yards with some "Airsept", a cooling coil coating treatment applied by spray (such as a garden sprayer.) This costs around $60 and can be bought from Volvo dealers as part number 000116154 or from GM dealers ("GM Cooling Coil Treatment"). I haven't used it, but it is supposed to result in a coating on the evaporator coils that inhibits mold growth.  GM claims good results. This procedure is described in great detail in the Volvo shop manual for heating/air/conditioning systems.  While you are at it, make sure as well that the cowl leaf screen is in place to limit ingress of crud which will be caught in the plenum and result in mold growth.

Interior Water Leaks: Clogged Evaporator Drain.  [Tips by Steve Seekins, courtesy of Guri Roesijadi]  [Query:]  Water is leaking into my front footwells and soaking the carpets.  How do I diagnose this?  [Response:]   The 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.  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 comes off.  There are plastic pins on each side that fit into slots on the cowl.  It also fits into clips along bottom edge of windshield.

Screen is fastened to underside of cowl with some sticky black RTV type stuff.  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. Get the plastic leaf/snow guard from Volvo that goes over the vent opening - helps keep the leaves and crud out.

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.

Heater Not Working.  [Query:] 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.
 [Response: Dennis Hamblet]  Several suggestions:
1. Your thermostat needs replacement and your dash gauge is not reading correctly. Cheap and easy to put in a new thermostat to confirm.
2. Your heater core has a deposit of sediment or minerals restricting the flow of warm coolant in which case the system may benefit from a backflush.
3. The heater control valve has a blockage restricting flow and may be in need of replacement;
4. You have a vacuum leak which causes the heat vent control to work improperly.

Heater Core Leaking?  [Query:] I guess that the heater core in my 86 740 Turbo wagon is leaking cause I have antifreeze on the front floor. Is this as nasty a job as it looks?  [Response:] The heater core is a pain in the @#%&* to replace. 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 get some drainage from the A/C condensate line.  The control valve may have spring a leak. Check that carefully, along with the hoses, before yanking the core out.  [Tips from Bob]  I have done 2 heater cores on 700 series cars. It is rather 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 have done a lot of 700 dash/interior work and are VERY familiar with it, the job takes about 5 hours. If you are not familiar, 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.)

MCC Climate Control A/C Not Working.  [Query]  Our 940's manual climate control AC problem is in the control circuit. The 700/900 FAQ shows the relay cluster, but there is no AC or ACC relay shown. Does anybody know where it might be on a '94 940 (non Turbo), Halifax assembly? A relay socket would be a good place to trace further, and, the car being a Volvo, the trouble could even be the relay!

Diagnosis Notes.
[Response: Patrick Paul] If you have power to the pressure switch then all components before that are OK as far as turning the power supply off and on.  You can go to the electrical connector on the compressor and check if you have power there.  If yes, then your problem is the control unit.  Any loose solder on the control board lets just enough current flow for you to get a voltage reading.  But the amps are not enough to turn  the compressor on.  The repair is very easy once you find that spot in your control unit circuit board.  [Response: Abe Crombie]  The control panel with the knobs is the control unit. The electronics are part of the control. The a/c compressor relay on the 91-95 740/940 with the manual a/c system is integral with the control assembly. The relay usually isn't the problem, it is the solder joints from the connector to PC board or PC board to relay pins. The relay is soldered to the circuit board. When you remove the control panel you will see the metal enclosure for PC board. [Response: James Abercrombie]  The time delay for compressor start is integral in the electronics of this board so there can be a failure of the circuit that stops the a/c compressor that is not related to the solder connections, but this is very rare.

Re-Soldering the Control Unit PC Board.
[Response: Philip]  We had intermittant AC problems on our 94 940 turbo that were cured by resoldering a bad solder on the control board (behind the switches). As usual you need a magnifying glass to see the bad solder. Ours looked OK, but had a dark circle aound the outside. Re-soldered it and save $400 for a new one.  [Response: James Abercrombie]  There are no service parts for this unit. The wave solder process demons have struck this unit. The solder cracks at the points where the high current load is passed through the PC board connections. Soldering is usually all it takes.
[Tips: Patric Paul] Remove the radio.  Take off the cover on the front of the control unit.  It just clips on.  There are 2 or 4 screws that hold the CU in place; take them out and disconnect the CU. Remove the silver panel (clips and screws).  Take out the screws for the circuit board and examine it.  The faulty  solder spot is in the lower half, a little to the left.  Take your time  and you will get it done.  Don't overheat the circuit board while soldering.
[Response: Brian Oliver]  The A/C failure was caused by the solder joint between the AC relay and the HVAC contoller's circuit board, as suggested. All this stuff is integral with the HVAC control panel in the dash.  Once you have the panel on your bench (or kitchen table in my case), remove the black plastic cover to expose the circuit board mounting screws, take out the circuit board, and look for the cracked solder joint. Mine was easy to see, but I do know that they are not always so. Resolder, reassemble, install in car, and enjoy. These HVAC control panels can be fixed as long as you don't need parts. They are at least as repairable as Bosch relays. They are sturdily built, too except for this one badly designed trace on the circuit board. I am a physicist by training, but years of working in failure analysis in the telecommunications industry tells me that the solder joint in question is under-engineered. I just scraped away some solder mask to allow greater wetting area, which I think will help prevent future failures.

ACC Heater Control Not Working.  [Query:] Re 1987 765T; while at the dealer getting a new transmission put in, I also had them install a new heater control valve. The automatic climate control system will not put out any heat, at any setting...even with defroster on. The dealer believes the problem is a vacuum connection in dash. The heater control valve is not getting vacuum. Previously I pulled the glove box out and checked the vacuum hose and shutter doors there...they seem fine. The A/C works fine. Dealer says it is about an hourís labor to look in the center dash to find the vacuum problem. Can I do this myself?  [Response:] Several things could have happened, most likely because the dealer who put in the new trans broke a vacuum line or crimped one somewhere...if you had heat before the trans was put in!   I think there's a vacuum reservoir underneath the car, passenger side, up front...it's a plastic reservoir, should have a line leading to engine and one leading to passenger compartment.  Check for vacuum at the engine line and at the line leading to the passenger compartment. Fix as necessary. You might try putting straight engine vacuum or vacuum pump to line going to passenger compartment (there are check valves somewhere too, it IS a turbo engine!) and see if that actuates the heater valve/flappers.   The actual vacuum switch is pretty reliable, but I've had to replace the climate controller/computer on my 87 764T.

ACC Climate Control Instability.  [Query] Recently I have noticed that my climate control has a new personality; in fact, several of them.  Our early Spring days in Charlotte sometimes require heat, and sometimes a/c. My trouble is that the hvac system delivers heat, then coolness, then nothing, then more unpredictability. This happens when set to a temp or total heat or total cool. What's more, the system's ability to select the right venting for defrost, heat, a/c, etc. has also gone mad.  Anyone had this problem, or recognize the symptoms?  [Response: Abe Crombie] The manual on this version ECC contains no troubleshooting charts. It only has the list of fault codes. The fault code list contains no fault tracing either. Any fault codes that would impact temp regulation would make the A/C button flash on start up and this was not mentioned.
Does it not provide heat if you go to absolute last stop HOT and cold air if you go to the absolute last stop COLD?  These end points override the temp sensors. The temp knob being set to either full end point should make system default to the respective mode. If this isn't happening then the servo that moves temp door needs inspection. If the temp goes to the proper mode at end points but not in any other temp setting (normal operation as opposed to end point defaults) then the ambient sensor next to blower in blower case would bear inspection.

ACC Air Conditioning Sensor Not Operating.  [Query:] When its cold out, usually around 50 degrees, the air conditioning works OK. When its warm out, it doesn't  work at all. No fan, No a.c. I assume its one of the sensors, probably the one on the dash. Its a 3 wire affair with a small lens in front. The other one is in the ceiling light, but I don't think that's the one  giving me a problem. Any suggestions?  [Response: Abe Crombie] The solar sensor is not going to cause anything to fail to function on that system. It only makes the system go slightly colder when it's sunny. It sends no signal anytime it's dark outside.  The sensor next to blower motor may be at fault. Turn the air dist knob to face vent, the temp to full cold, fan in AUT, a/c switch off, and recirc on. Now punch the a/c switch on and then off and count the flash code, punch a/c switch again and repeat reading two more times. This will give any fault codes that are present in system. The sensor can be bad and give no code as the system doesn't know it is defective as long as it gives a reading that is within -50F to 180F. If it says it is 60 deg out when it is 96 the control unit doesn't know it is a bad reading.

ECC Climate Unit Diagnostic Codes.  The ECC climate unit in air conditioning-equipped cars can detect certain system faults and display the appropriate diagnostic trouble code by flashing the lamp in the A/C button.  If the control module detects one or more faults, the driver is warned by the flashing A/C button.  If a fault is major, the lamp will flash continuously while the engine is running; if minor, the lamp will flash for 20 seconds after the engine is started.  To read the diagnostic trouble codes, the engine must be running; the blower selector in AUTO setting; the function selector in VENT setting; the temperature switch set to maximum cooling; the recirculation switch pressed in; and the A/C switch released (out).  Shine a strong light on the solar sensor in the dash speaker; otherwise, the DTC for the sensor will be displayed even if fault-free.  Retrieve the DTCs by pressing the A/C button in and releasing it within 5 seconds.  If several DTCs are stored, they will be displayed sequentially.   All will be erased when the ignition is turned off.  If no faults are set, then "1-1-1" will be displayed.  Note that faults may be in the component or in its wiring.

To diagnose cars with ECC but without air conditioning, no trouble light will illlumine; the system will fail.  Remove the ECC module from the dash panel, take off the cover plate and press the diagnostic test button twice within 5 seconds.  Read the DTCs from the nearby LED lamp, pressing the button after each DTC to read any more codes.

Table of ECC Diagnostic Trouble Codes.

[Fault Classes: A: Serious;  M: Minor;  I: No warning to driver]
Fault Component & Description
Fault Class
  Ambient temperature sensor (on blower housing):  
  Short-circuit to ground
  Open circuit or short-circuit to 12V
  Interior temperature sensor (in roof light):  
  Short-circuit to ground
  Open circuit or short-circuit to 12V
  Coolant temperature sensor (in heater):  
  Short-circuit to ground
  Open circuit or short-circuit to 12V
  D+ signal level in generator
  Solar sensor (in speaker grill)  
  (Note: illuminate this with a lamp to clear code)
  Open circuit or short-circuit to ground
  Short-circuit to 12V
  Servomotor Drive:  
  Pin 17 or 18 connected incorrectly to 12V
  Motor activated for too long > 10 seconds
    (blocked motor or failure of motor supply)  
  ECC Control Panel:  
  Faulty temperature control
  Blower Motor:  
  Starting current too high, motor seizes or
    turns sluggishly  
  Power terminal incorrectly connected to  
    12 V for the solenoids as follows:  
    Water valve
    Maximum blower relay
    Blower relay (cars with air conditioning)
    Engine cooling fan relay (cars without a/c)

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