Auto Air Conditioning Repair

I have worked on auto air conditioning repair for years and I get lots of questions sent in from my readers every month.

Your auto aircon system is made up of many individual parts -  compressor, expansion valve, receiver/drier, accumulator, AC lines, condensor and pressure sensor.

To troubleshoot, repair and maintain your vehicle, you'll need diagnostic and repair information that is specific to your car or truck. For this I personally use and recommend ALLDATAdiy. With full manuals for over 30,000 vehicles online, you will find an exact match for your vehicle's year, make and model.

Besides being cheaper than a factory manual, they also offer step by step repair instructions and detailed diagrams beyond what is found in most printed manuals. Click here for a sample of their diagnostic and repair information.

Answers to Your Auto Air Conditioning Problems

You will find my answers to most of the AC repair questions that I get from my visitors below. They will help you diagnose the possible problems with your air conditioning system and pinpoint which parts are faulty.

If you still have any unresolved vehicle problems or questions, you can ask an auto mechanic online. For expert answers specific to your vehicle's make and model, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee and you can also browse their answers to other users for free.

Air Conditioning Compressor Burned Up

My A/C compressor burned up. What do you recommend I have replaced? I've been told everything from compressor and orifice tube, to the whole system. (1999 Chevy Silverado 2500)

Answer: Thanks for sharing your auto air conditioning problem. At minimum I recommend that the compressor, orifice tube and the accumulator be replaced and when that is done the whole system needs to be flushed out.

Since the old compressor was faulty it is likely that it put all kinds of debris through the AC system. This is why some people say that you should just replace it all. If this debris is pulled into the new compressor it can cause it to fail very quickly. I have found that flushing the system works well for getting the debris out.

It is very important to use a mechanic who is experienced with auto air conditioning repair because it can be hard to get everything out.

One other thing you could to is have them install an inline filter as a precaution just to be sure that nothing gets to your new compressor. Auto air conditioning systems are very susceptible to debris.

Air Conditioning Clutch Rattles

1997 Ford F-150 4.6L. The A/C clutch rattles real bad and has started smoking. Is the problem the clutch or something else causing it. Thank for your help, Ray.

Answer: There are several things that can cause this type of auto air conditioning problem. The first thing that might cause it is a bad clutch. If the compressor clutch is simply worn out it can lead to rattling.

It is also possible that you have low voltage to the clutch which might be causing it to not be able to completely engage or disengage. There could be a pressure switch or other wiring problem that could be causing this.

You AC system could have very high pressure and cause your AC clutch to slip. This is not likely because most AC systems have high pressure cutout switches to prevent this, but it is possible.

These are the most likely causes of your auto air conditioning problem. This is something that should be repaired right away because it could cause costly damage to othe parts of your system.

A/C Blows Hot Air Under Hard Acceleration

Hi, I have a 1998 Ford Ranger, V6, 4.0L Automatic, A/C. When I go up hills or under hard acceleration, the A/C starts blowing hot air. It does start to cool down for about 1-2 minutes after I'm done accelerating. What the heck!!!

Answer: Hi, RC. What you are describing is completely normal and there is no need for auto air conditioning repair. This is a strategy used by the computer to give your truck plenty of power when going up hills or when it is floored. The AC system takes a lot of power to run so the computer cuts out the AC during these times.

A/C Blows Out Hot Air Under Normal Use

1. Why does my a/c blow out hot air? ... for the past year or two i have had to put my a/c on full blast in order for it to blow out cold air and stay on, I am always having to hold down the button for it to blow out air from the a/c unit because other wise it will switch on its own to blow out air from out side.

Just recently, like the past two days I noticed that it has been blowing out hot air only even w/the button for it to blow out air from the inside unit and not the out side.

What can I do?.... Do you think putting in Freon will solve the problem? FYI: I am a girl, so sorry if the questions seem dumb or don't make sense I really know nothing about cars. (2003 Chevy Malibu)

Answer: Thanks for submitting your question. The majority of questions I get are from females and that is one of the main reasons I created this website so don't feel bad about not having a lot of car knowledge. You are doing the right thing by trying to learn about your car!

From the description it is hard to tell what might be going on. I think the most likely cause of your auto air conditioning problem is probably the control unit. This is the part that has all the buttons and switches.

The only way to really know is to take your car to a mechanic to have it diagnosed. This is probably not what you wanted to hear, but without being able to test it myself there is just no way for me to know what exactly the problem is.

It is most likely not a problem with low refrigerant, but if you take it to a repair shop they can see what the pressure inside your AC system is and that will tell them if it is low or not.

2. I had a free air check on my 1995 Maxima. I was told it was fully charged and should be working. It blows out hot air instead. The guy I bought it from 6 months ago said it worked great last summer. Do you know what the problem might be.

Answer: There are many things that can cause your A/C to not be working. It is impossible for me to tell which ones might be the problem for your car without having more information.

The best advice I have for you is to take it to a different shop. There is obviously something wrong with your auto air conditioning system. If there really is enough refrigerant then you are probably looking at an electrical problem. There is probably a faulty switch or something that is not letting the computer turn on the compressor.

3. I have a 2005 Nissan Sentra. My air conditioning unit stopped working. The unit was blowing warm air. I took it to the repair shop, and was told that it had a slow leak and I had to replace the unit.

The air conditioner was replaced, and it worked fine initially. The replacement was done on 2-27-2009. However, slowly the unit started blowing warmer air. It the morning, it blew a cool air; on the scale 1 to 10, around 6. But by noon, and afternoon, when I am drove home from work, it blew warm air.

I took the car to the shop on 7-10-2009 in the morning. Explained the problem to the technician. The air conditioner was tested, and I was told everything was fine. I advised the technician that it was not fine. He decided to recover the Freon and recharged the unit again. Saying, that maybe there was air pocket causing the unit not to work properly.

At the repair shop the unit worked ok. I drove my car around the next day, and again the air conditioner started blowing warm air. I do not know what to do. The last time I was there the mechanic gave me impression that I was wasting his time and I did not know what I was talking about and the unit was fine. I paid almost $1100 for the new air conditioner for 2005, Nissan Sentra.

The replacement unit worked ok for about 4 months. I am out of the money I paid for the new unit and the unit is not working. Please help. Thank you. Janusz

Answer: This sounds very frustrating! This auto air conditioning repair needs to be done by the shop that did the original work. It sounds to me like they don't want to take the time to diagnose your auto air conditioning problem.

What they need to do is first verify your complaint. They need to drive your car around until they can see exactly what you are talking about. Until they do that they will just be stabbing in the dark trying to figure out what is going on.

If needed, talk with the manager at the shop and remind them that you just spent $1100 to get your AC fixed and it is not fixed. If this shop is worth anything they will take your car, verify your complaint and repair it correctly. If they are not willing to do this then take your car to a different shop and report this one to your state's attorney general.

A/C Won't Cool

My ac in my 1997 Ford F150 4.2 V6 is not cooling. When the AC is on, or the heat, the vehicle idles fast. I used one of those gauges that comes with cans of freon to check my pressure and it looked OK. Any guidance would be greatly appreciated.

Answer: There are many things that can cause your ac system not to cool properly. The first thing that I recommend you do is take your truck to a repair shop to have them check the AC.

Those gauges on the little cans are a big scam. In order to know much about the AC system you have to know the pressures of both the high side of the system and the low side of the system, and how often the clutch is cycling (if it is a clutch cycling system). Just because the can gauge says it is OK does not mean that it really is.

The most likely cause of your auto air con problem is either an incorrect refrigerant charge or an electrical problem. You could have a bad pressure switch or even a bad relay or compressor clutch. It is normal for the engine to rev up a little when the AC is on so that is probably nothing to worry about.

A/C Hardly Blows

When I start the car and turn on the air conditioning the cabin fan starts off at full volume, then starts to decrease in volume, as time goes on til almost no volume, but the air is still cold? (1994 Pontiac Firebird V-6)

Answer: There are two things that come to mind first. The first is that you might have a plugged or dirty cabin air filter. Not all cars of this year have them so check your owner's manual. If you don't have a manual then you can see if there is a removable plastic piece under the dash. That should be where the air filter is located.

If that does not fix the problem, then there is a good chance that you have a plugged evaporator. Condensation builds up on the evaporator and eventually it can start growing mold which will build up and plug it. Most auto parts stores can get you something to get rid of it.

A/C Vents Emit Rattling Sounds and Foul Smells

I have a '97 Dodge Stratus, 2.4 L engine, that has had a good A/C unit working just fine up until a few days ago when I turned on the A/C, a uniform rattling noise comes from the right side dash area and glove box. The two A/C vents on that side are still blowing cool air like it should, except with that annoying rattling noise that is rhythmic and sounds like it's something wrong with the fan.

Also it's emitting a foul odor that is all along the lines of a dead rodent, wet dog, and garbage that's been sitting in the sun for a few hours. Again, the air still works, but I really hate the smell and of course the rattling noise. Also when I turned up the A/C, the rattle got louder and more frequent, which again makes me think it's something to do with the fan. The sound goes away completely whenever the A/C is turned off.

Answer: Hi, Ethan. Thanks for submitting your auto air con problem. The most likely cause of your problem is your fan. I can't think of anything else that would have those symptoms other than the blower motor.

The smell you are getting is likely caused by some type of mold that has built up inside your auto air conditioning system or on the evaporator. Most parts stores have chemicals that you can buy to remove it. If you cannot find any, then you should check with your dealer or a auto air conditioning repair shop.

Vehicle Stalls with A/C On

I have a 2003 dodge ram quad cab 4.7 liter engine. I just replace the AC condenser fan on it cause it went out. Now when I cut the AC on while driving and come off the gas and come to a stop the truck falls dead. I have checked fuses, no lights are on, or anything. This has stumped me. Could you please help?

Answer: I believe can help some. There are several things that might be happening here. If your idle air control valve (IAC) is not working properly it could be causing this problem. Also, your cars computer could be causing the problem or it could just be a wiring problem somewhere.

Since you have recently done some work to your car the first thing you should do is re-check that you have everything connected properly. It is possible that something was just left disconnected.

You trucks computer is supposed to turn the idle up when you have your AC on so it does not die like it has been doing. The hard part of this auto air conditioning repair is figuring out why.

A/C Blows Weaker During Long Trips

I have a Ford 2004 Explorer which just had the evaporator core, line and condenser replaced. The system blows cold air, but when driving for a long time on the freeway the air does not blow very strong. This only happens on long trips. The fan sounds like it is blowing but is not coming out the vents. Can you help. Thanks!

Answer: The first thing to check is your cabin air filters. If they have not been replaced in a long time you should just replace them. I have seen them so dirty that air would hardly flow through them and caused the same problem that you are having.

Be sure that there is nothing clogging the cowl (the part at the base of your windshield on the outside that has slits in it for air to get in) and make sure there is nothing blocking the passenger side footwell.

If none of this helps, you might have a problem with one of your air divertor doors. If it is not working correctly it might not be letting enough outside air in. This is not likely but possible.

If the problem still persists, then you should have it looked by an auto air conditioning repair shop.

Air Conditioning Condensor Doesn't Shut Off

My 1999 Dodge Dakota AC condenser I believe will not shut off. With the controls on Defrost and Foot with the dial turned all the way to hot, I can still hear the part of the AC in front of the engine spinning on. I believe this is hurting my gas mileage. I cannot get it to turn off. How can I turn it off??

Answer: This is simply what AC systems are made to do. When you turn your controls to defrost the AC actually does come on, but it does this to dry the air not to cool it. Even though the AC system is running, it actually does not cool anything because the heater is on. If you don't want your Ac system to run, you cannot have it on defrost.

A/C High and Low Sides Aren't Balanced

We recently changed the A/C compressor and the line with a new orifice tube but are still having problems getting the high and low sides to balance. Any Suggestions? (1998 Ford Mustang)

Answer: I'm a little confused as to what the problem is with your auto air conditioner. The high and low sides should not balance. With the AC on and the car running the high pressure side should be much higher than the low pressure side.

The only time when the two sides should balance out is when the engine and AC system are off and the car has sat for a few minutes. If it does not balance out then there is probably a restriction somewhere in your system.

When it comes to AC systems, I always recommend having your auto air conditioning repairs done by a good AC technician. I know this is probably not what you want to hear, but it would save you a lot of time and probably some money too.

A/C Switches Between Hot and Cold

Several years ago, I got in my car and turned on the heater and turned the temp control on the dash board over to hot. As I was turning the control to hot I felt something snap. It was stuck on cold and remained that way for sometime. Eventually it flipped itself over to hot. Even if the AC is on, the air is hot.

Right now it's stuck on cold, which works since it's summer time but if I were to turn the fan too high, it will flip back to heat. I know this involves removing the dash board. I was wondering if you had an idea of what parts might need to be replaced and what I can expect to pay for an auto air conditioning repair like this. (2000 Dodge Stratus)

Answer: Hi, Brett. Thanks for asking me your question. There are several possibilities that could be causing your auto air conditioning problem. The first and most likely is that the cable that controls the heater valve might have broken which would allow the valve to move open and closed freely.

It could also be a problem with some of the linkage under your dash. You might even be able to see it if you look. It could also simply be a problem with the heating and cooling controls.

I don't know what the cost of repairs would be because there are many things that could be wrong.

If you are lucky the dash will not have to be taken apart and the repair would probably be in the few hundred dollar range. If it was a more serious problem it could be more. I'm sorry that I can't be more specific. When you take your car to the repair shop you might want to have them just diagnose the problem and give you an estimate for the repair. That way you can save up some money to have it done if needed.

Erratic A/C Blowing

When we push the gas it stops blowing air through the vents but still keeps going through the dash, and when we brake or come to a complete stop it starts blowing through the vents again, why is it doing this?, and it is cooling it's just not blowing through the vents when we take off. We appreciate all of your time. Thank You, Mr.and Mrs. V (2001 Ford F-150)

Answer: Hi, Mr. & Mrs. V. Much of your hvac system is operated using engine vacuum which is at its highest level when you are idling or you take your foot off the gas. Since this problem auto air conditioning happens when there is a small amount of engine vacuum, it is most likely a problem with one of the vacuum valves that makes the blend doors move to the correct position when you move the controls.

You can look under your dash to see if you can see any hoses or lines that are not connected, but most likely you will have to take this to a repair shop to have them diagnose exactly where the problem is.

A/C Lacks Cold Air

We have a 1998 Ford F150 and the air conditioning isn't working properly. It won't kick in until the car starts moving, and then it only work for the first 5 minutes then start blowing hot air. Could it be that we just need freon? And if so, does it take the new or old kind of freon?

Answer: It is definitely possible (and quite likely) that you just need to have more refrigerant put in. You truck should take R-134a. I highly recommend having a good repair shop do this because it is easy to put too much or not enough in. Also, if you use the wrong type then not shop will work on your auto air system in the future because the refrigerant will be contaminated.

If it is low then you should have your truck checked for leaks. If it is just leaking the refrigerant out then you will be wasting time and money putting more in until you get the leak repaired.

A/C Starts and Stops Intermittently

Hi! I have a 1996 Toyota Camry that has some sort of A/C problem.

When you turn the A/C on, it would light the light on the auto air button, you can hear the car rev up signaling that the compressor has coupled, but after 4 or 5 seconds, the car comes back to the idle revolutions as if you had turned the a/c off, and the light on the a/c button starts "flashing" (when the a/c was ok the light would only turn on if it was in use or off if it was turned off)

I already got the service manuals for the a/c, but I don't see any kind of computerized control, just a few temperature sensors and relays. The refrigerant is full (got it checked). Do you have any idea of what could be checked in the a/c system? thank you!

Answer: Hi, Diego. It's good to hear from Panama today! The most likely cause of your problem is a fault with one of the pressure sensors or maybe even the relay. It sounds like the pressure is good when you first start the car so the compressor comes on, however either the pressure sensors are not working right or the relay could be not sending power to the compressor after those first few seconds.

The switches are easy to check. Just see if there is power going to them, then see if there is power going out of them. Keep tracing the power back to wherever it stops and you've probably found your auto air condition problem.

Air Conditioning Clutch Doesn't Engage

The clutch will not engage on this car even after changing the a/c fuse. What else can I try before I have to take it to the shop? (2006 Chevy Impala 3.9L)

Answer: Since your AC fuse is blowing that means that there is some type of electrical problem with your system. This would be a very hard thing for most people to figure out. About all you can do is check all of the connectors and wires that you can see for your AC system. Other than that it should probably be looked at by a professional technician.

Since the clutch never engages you might have just the one electrical problem of you could have other auto air conditioning problems such as pressure switches that are faulty or a low refrigerant charge that are causing the clutch not to engage.

A/C Not Working at All

I put a rebuilt ac compressor on my truck. Everything looks to be working, but when I go to turn it on it wont work, I checked the fuses and they look good. What should I check next? By the way the ac has been charged! (1994 Toyata 4Runner)

Answer: There are many things that can cause your auto air conditioning problem.

The first and most common is that there is an incorrect amount of refrigerant in the system. There are high and low pressure cutout valves that will not let the compressor turn on if the pressure is too high or too low. It is also possible that your A/C controls are not working properly, but that is unlikely.

I highly recommend that you take your truck to a repair shop to have them look at your air conditioning system. If you did not flush the system before you put the new compressor on then that needs to be done. Also, if you did not evacuate the AC system for at least 30 minutes then there is probably still air in the system and that will cause many problems.

If I had to guess, I would say that you are having a low pressure or high pressure problem either caused by too much or not enough refrigerant... or debris that has plugged part of the system.

A repair shop will be able to diagnose and repair this problem much faster and probably cheaper than you can. I would suggest leaving auto air conditioning repair to the professionals in your case.

Vehicle Overheats with A/C Running

When I drive down the road, the truck temperature start, to move toward hot. I turn the air off and it helps. The blower will stop running at times. I had it fixed once it is doing it again. Could this be the problem? (2006 Chevy Colorado)

Answer: If by blower you mean the cooling fans in the engine compartment then yes, this could be the problem. The cooling fans should always be on if the auto air conditioner is on. If they are not then that is most likely your problem.

You should check to be sure your coolant reservoir is full and your radiator as well. If either are low then you should refill them using the factory specified coolant.

It is very important that this gets fixed because if it doesn't and your vehicle overheats it could cause major engine damage that could cost a lot to repair.

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