Repair Topics/ Air Conditioner-1 / Air Conditioner-2 / Air Conditioner-3

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Car Air Conditioner Questions and Answers

This category contains featured questions as examples and relate to most vehicles.

Question: 1998 Pontiac Grand Prix 3.1. It has the heavy duty cooling system (2 fans). The AC hasn't worked in a long time and I recently discovered that the cooling fans are not working either. I don't know how long ago they stopped working. When I put the car in diagnostic mode, both fans come on fine. Looking at my Haynes manual (severely lacking in electrical logic) it appears that the computer grounds the coil on the relays to activate the fans and A/C compressor. I opened up one relay and clipped a test wire on the computer side of the coil. As soon as I grounded it, the AC compressor came on. I moved that relay into the other sockets for each fan and I could turn those on as well. As best I can tell, the computer isn't getting something it needs to turn them on. I don't feel the computer is messed up since it will turn them on when in diagnostic mode. There are no codes on the computer. The temp gauge works fine. I just flushed the coolant and the low coolant sensor appears to work as well. What should I look for next and what would be the test procedure? This is not my daily driver but will be once Firebird hibernates for the winter.

Answer: It sounds like you have a bad temperature switch. It is located on the lower right rear of the engine. Don't confuse it with the temperature sensor for the computer which is located on the top rear right of the engine.

Follow-up: Took the car in last night to get the cooling fans fixed and replace the stolen lights. The dealer just called, here is the deal: The fans work fine and come on at 228 degrees.... but the gauge on the cluster reads 260 (basically pegged) at that point. The problem is the gauge is hosed and it is $200 to whatever to get it fixed, or many much more to get it replaced. They changed me $30 bucks to give me that information. Not too bad... but who would have thought it was just a messed up gauge the whole time. I will most likely install an aftermarket gauge. Thanks for all the help.

Question: 1995 Plymouth Voyager 125,000. You fellows have a really great site! I hope you have an answer to my problem. I bought the above-mentioned van used. About six months later, the a/c compressor quit. I replaced the whole assembly not knowing the history of the vehicle. Upon further checking, the compressor clutch coil had fried. This was with R-12. After replacing the whole compressor using 134a, the van cooled fine for a couple of months. Then the coil went out again. The compressor was still under warranty, so it was replaced. This coil lasted about two years. About a month ago, this coil went out. It also took the clutch plate, so I thought that maybe that was the real problem. I replaced the whole clutch assembly. It didn't last three weeks. This time it was so bad, the compressor bearing was in pieces when I took the assembly off. Please help if you can. This is getting really nerve racking, not to mention expensive! The head pressures appear to be correct. I am installing about 30 oz of 134a when I evacuate and recharge the system. I hope this is enough info for you to give me at least an idea of where to start.

Answer: Try flushing out the entire air-conditioning system and replacing the receiver-drier and the expansion valve.

Question: 2001 Dodge Grand Caravan LE 74,000. Hi Guys! Interesting site here, but don't see a reference to my problem. My A/C system vents pop over to the defrost vents when I accelerate. I went to a Chrysler dealer; they sold me this small black vacuum reservoir to put in line with the vacuum line that runs from the master cylinder to the control. This temporarily made a difference, now the problem is back. I went to a salvage yard and got a large vacuum reservoir off of an older Caravan, but this doesn't help either. I have looked at all the vacuum lines, especially the main ones, nothing seen there. I don't have a vacuum gauge but suspect a leak someplace. Think the control itself is a culprit? Any common problems with this in Caravan that you know of? The dealer said they all did it.

Answer: Somewhere in the vacuum supply to the Air conditioning controls is a check valve between the engine and the reservoir. The purpose of the check valve is to eliminate the problem you are having. Your check valve may have failed or you have a vacuum leak somewhere in the system.

Question: 2002 Ford Taurus mileage: 69,000. Heater is not working. A few weeks ago, it was working fine. Now when I turn the temperature dial from cold to hot it remains cold. I can feel the air change directions as I change from Def. to Def & heat. Nothing is wrong with the heater core, no leaks of any kind. Heater hose gets hot to the touch. I believe this is a vacuum or elec. problem. Could it be a damper is not closing or opening to force the fan to blow over the heater core vs. A/C? Not sure (can't see) where the vacuum lines are on these newer vehicles. Do you have any suggestions?

Answer: The air-conditioning/heating controls are not vacuum controlled but are controlled by electric motors. You may be experiencing problems with the monitor that controls the blend door temp. Enter into diagnostic mode to check for trouble codes.

Question: 1999 Continental, Lincoln v-6 Liter mileage: 84,000.  When my compressor engages the A/C system works very well. The problem is to get the system to engage the clutch.  The vacuum motors all seem to work appropriately.  The temperature selector seems to work ok.  When you vary the temperature selector up or down the vacuum motors, doors and blower act appropriately.  The heater works ok.  Every button on the control panel works, as it should.  But when the system demands cooling the compressor may or may not come on.  When you select AUTO, MAX, FLOOR/ PANEL or DEFROST the compressor may or may not come on.  The temperature setting seems to have no effect on getting the compressor to engage.  For some unknown reason and at an indeterminate point in time it will decide to engage the clutch and the system works well for the rest of the trip.  But shut off the engine and start it again and the compressor clutch may or may not engage.  I have checked the plug-in at the clutch and when the clutch is not engaged there is no power there.  I do not know where the clutch picks up its ground.  I have found 3 grounds under the hood and they all have continuity.  When the car is not running and the ignition is off, I have removed the plug to the clutch the plug then seems to have continuity to ground from either or the two pins of the plug-in.  This intermittent problem is driving me nuts.  Do you have any ideas?  Thanks, Kevin

Answer: Yes, we just had this problem in the shop and this is what is happening, the compressor is controlled by a pressure switch that is on the accumulator is has electrical contacts that malfunction. Replace the low side pressure cycling switch and retest.

Question: 1999 Honda Civic mileage: 112,000.  I have a Honda Civic 91,142 miles. My A/C works fine first time you turn it on.  Runs for 10 min then stops cooling.  I got it checked out.  There were no leaks in the system.  The mechanic's guess was, compressor doesn't turn on when it is hot.  He gave me an estimate of $1100 to replace the compressor, receiver dryer, evacuate, recharge etc.  Is this the only way to fix the problem?  Could it be something else that causes compressor to stop when it is hot?  I would appreciate it a lot if someone could help me out.

Answer: When the air-conditioning compressor stops working, check the voltage to the clutch coil. If ok and the compressor is working check the cooling fans to make sure they are on. If ok, have the refrigerant levels checked.

Question: 2004 Cadillac Deville 5.2 mileage: 40,000.  I have a very strange electrical problem.  The A/C blower fan continues to run at high speed even when the Air Conditioner / Heater control is turned off, and more importantly, even when the ignition switch is turned to the off position.  Any suggestions?

Answer: The blower motor is controlled by a speed control module that is probably shorted "on" causing the blower to run all the time.  Replacing it should fix your problem.

Question: 1999 Mazda RX7 54,000.  My car makes this loud squealing noise when I start it and then it stops. I was told it was my air conditioner belt, but I had it looked at and it wasn't worn so they put some belt dressing on it and it stopped, for awhile.  Now it's squealing even worst even when I'm just stopping at a red light.  What should I do?

Answer: You will probably have to replace the air-conditioner belt.  Once a belt starts to squeal the sides of the belt glaze over and no adjusting or treatment will permanently stop the squealing.

Question: 1998 Ford Probe mileage: 75,000.  I live in Minnesota where you don't use the air conditioner during the summer.   Last week it finally got warm enough.  When I try to activate it nothing happens.  Well, something does happen.  If the car is at idle, it will rev up slightly as if the car is expecting to be bogged down.  That's it.  I don't hear the compressor engage and I don't hear the engine bog down.  I've checked the fuses.  The AC was working fine last summer.  I'm willing to have it looked at by a professional, but want to exhaust my own options first.

Answer: Your air-conditioning system may be low on refrigerant.  The compressor will not engage if the system is low on refrigerant due to the low-pressure cut-off switch.

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