Air Conditioning Auto Repairs
Sometimes air conditioning auto repairs are not as complicated as they may first seem. Let me give you a quick example of what I’m talking about.
A customer recently visited me for a car air conditioning repair. He informed me that the air conditioning stopped working towards the end of the warm weather in 2008.
He thought for sure that this would be an expensive problem and decided to hold off on the diagnosis and repair of the air conditioning system until the warm weather returned. This is probably what most automobile owners would do in this situation.
Automotive air conditioning diagnosis
My first step in any auto repair troubleshooting is to perform a visual inspection. But I let myself down and did not perform this step. In my mind I thought that the Freon had leaked out, and that’s why the compressor was not coming on. This is the most common situation when it comes to automotive air conditioning not blowing cold air.
I connected my manifold Gauges to the air-conditioning system. I found that not only were the pressures the same on both sides as they should be with the compressor off, but the vehicle currently had a full charge of Freon. My customer was buzzing around me trying to figure out why I had a surprised look on my face.
I said to him, I have good news and bad news. The good news is your air-conditioning system is filled with Freon and ready to blow cold air. The bad news is the compressor is not coming on and it is apparently an electrical problem.
My customer said oh my god, not an electrical problem. I said calm down and let me start poking at it and see what I find. I checked the air-conditioning fuse and it was good. So I returned to my normal diagnostic procedure. I performed a visual inspection of the electrical wiring and connectors to the cars a/c system.
Air conditioning auto repairs
A/C Compressor
I had the key on engine off and decided to check for power at the A/C compressor. When I grabbed the electrical connector, which was a two wire simple power and ground connection, the compressor clicked on and engaged. So the problem turned out to be a poor connection to the air-conditioning compressor. No actual parts and a very small amount of labor repaired the A/C system.
But that is not the end of the story. The reason for the poor connection was that the connector was actually damaged. The plastic housing that holds the terminals had a crack in it and allowed the terminals to back out. I question my customer about how strange this was that there was damage to this connector.
My customer said, oh I forgot to tell you. Last year my belt broke and I had it replaced while I was out of town at a local gas station. So actually what happened was when the belt let loose it damaged the air-conditioning compressor electrical connector.
But yet another lesson to be learned about air-conditioning auto repairs. It is not always a good idea to put off diagnosing and repairing this system even if you will not be using it for months. My customer knew that his air was not working and suffered with his dark secret all winter long.
He actually told me that he was dreading that summer was approaching, because he knew the A/C repair would be necessary. So why spend five or six months worrying about something that may be repaired very easily. Also if the situation was different and there was a major A/C leak and the system was left empty for that long, further damage may have occurred and increased his auto repair costs.
This story is one reason that I decided to post a DIY auto air-conditioning repairs section to my new car repair website. You will find many pages that will not only explain the theory of operation, but also discusses common automotive air conditioning problems.
Mark Gittelman is an ASE Certified Automotive Master Technician With more than 24 years experience in the auto repair field.
MY A/C STOPPED BLOWING COLD AIR. MY MECHANIC PUT SOME GREEN DYE COOLANT IN IT AND IT SHOWED NO LEAK, THE COMPRESSOR CLICKS ON AND OFF, I JUST PUT IN SOME COOLANT AND LEAK SEAL SO I’M GOING TO SEE WHAT IT DOES NOW. THE COMPRESSOR RUNS FINE WITH THE DEFROSTER ON. WHAT IS YOUR OPINION ON THIS OR DO YOU NEED MORE INFO THANX SCOTT VOYLES
Hello Scott: This sure is a strange air conditioning problem. The fact that the compressor stays on only when in the defroster mode is bizarre. The subject of my post was air conditioning auto repairs are not always complicated. But in your case it appears to be complicated.
My next step If I was diagnosing your vehicle would be to connect a manifold gage set to the high and low side service ports. Then monitor the pressures. Your car ac may have a restriction or a clog in it. The best way to check for this is to monitor ac system pressures.
Hi I filled up my 99 Pontiac grand am with a freon and it works great for about 2 or 3 weeks. Then the air started to get warmer. I am assuming it’s a leak. If it is a freon leak how can i resolve the ac problem.
Hey Marc: I put together a page that talks about what to do with a small freon leak. There are several ways to handle car air conditioning leaks.
hi i filled my 99 grand am gt up with freon the compressor runs fine but my a/c fan wont kick on and the air is not really cold what could the problem be thanx
If you are talking about the ac condenser fan not working? It could be a bad fan motor itself. I have seen this often. But the best bet would be to follow a diagnostic tree chart for the ac fan inoperative. This will test the circuit that sends power to the fan motor.
Running into the same issue on 99 Grand Am GT. Put gauges on and system has pressure. Cannot get compressor to engage. Checked Relay, (swapped with horn relay) changed one fuse (10 amp for AC was blown).. Switch light in dash glows as if it is getting energized, What other electrical back yard mechanic checks can be done?
Any check for high side switch? Check for BCM activating relay?
Thanks for any help..
Mark on Your 99 Grand Am ac problem you mentioned the fuse was blown. If you replaced it and it didn’t blow again? I would have someone check for power at the compressor.
If you do have power at the compressor clutch with no engagement it could be a bad clutch coil. I have seen this before where the ac clutch coil takes out the fuse when it goes. It was not on a 99 Grand am though. And it could be a lot of other things as well just thought I would mention it!
I put up a video I recommend for basic electrical diagnosis tips. The video actually shows you how I use automotive wiring diagrams to fix electrical car problems.
The AC in my 99 Grand Am also only blows warm air. I took it to a mechanic and they checked for leaks and evacuated the system. Now they are telling me that it is an electrical problem. They say I have to replace the ECM (electronic control module) and have it reprogramed but I am not sure about this. What do you think?
Thank you.
It is possible for the ECM to cause the ac not to work. It’s rare but I have seen it before on a Grand Am. What makes me think that a second opinion is in order is the fact they evacuated the system.
If the clutch was not engaging do to an electrical problem, the shop should have never touched the freon side of the ac system. They could check pressures without evacuating. Second opinions on expensive repairs is always a good idea.
I have a 1997 Lincoln Town Car, the air compressor won’t come on. If you put 12 volts to the low pressure switch it will come on and blow cold air, as soon as I disconnect the wire it quits. Are there any other switches or sensors to check? Thanks
Melissa: Sorry I would have to see a wiring diagram. If the Town Car has automatic climate control that system can be quite complicated. If you do have ATC the factory auto repair manuals are the best way to go. They will have diagnosis and repair diagrams for the electrical side of the system.
I bought a recharge kit – 2 cans of R12 and gauge and R134 fitting with blue cap. The low side went from 30 pounds to the recommended 38 pounds, but when I removed the quick coupler, I discovered that the valve was damaged in the process and leaks. So I replaced the valve. This was not done quickly because of rust in the stem. I lost some refrigerant ( and maybe some mineral oil? ) When I tried to recharge the system again, the low side would not go below 90 pounds. Do I need to add mineral oil? Is there an air lock now? Would I have better luck at night when it is cooler outside? What do I do?
Hi Mike: It does sound like you have air in the system. It would most likely need a evacuation and then recharge at this point. I put together a page that describes the car ac recharging procedure. http://www.youfixcars.com/car-ac.html
i bought a 97 lincoln towncar it was in a crash i need to know how many lbs of freon it holds
thanx
Rick: If I can’t find the freon charge capacity on an under hood label I usually start with a 2 lb charge, check pressures and add from there. I have worked on a few 97 town cars for ac problems and I think that the charge is 2.4 lbs but don’t quote me on that.
I have a new Honda Civic, it blows cold air when accelerating, but it warms when deaccelerating. Honda says that is normal ?
This is after they evacuated and rechaged sytem (added.76 lbs) because it was never cold from the factory.
I have experienced warm air when increasing speed (on small car) because shutting off the compressor helped acceleration. The oposite doesn’t make sense to me.
HELP
The air-conditioning was working okay. But, now when I turn it on, the a/c knob lights up for about three to four seconds and then starts flashing. Now the compressor will not work.
I live in South Florida and have a 2005 Jeep Liberty. A/C worked fine until last week when the a/c just suddenly started blowing warm air. However, when I accelerate it starts to blow cold again. It only blows cold during acceleration. I looked under the hood while the engine was in park and at idle. Found the clutch engaging and disengaging in 5-10 second intervals.
I used one of those cheap gauges that come with a charge can i had lying around from a previous vehicle and it read full charge. I need help.. Its so hot and humid down here. Money is so tight that i am afraid to go to a tech.
Luis: It sounds like maybe a condenser fan type problem. The faster you go the more air that flows across the condenser. Its the job of the condenser fan to pull that air across the condenser at idle.
Without air flow across the condenser the high side pressure shoots up. The cycling clutch would be a symptom of that also. The high pressure cut off will disengage the compressor to prevent damage from high pressures.
Hi! I was driving today and my AC suddenly stopped blowing cold air. I had someone help me put freon in it. As we were doing it, the air would seem to start to get cooler and then would stop. Once the car appeared to not take anymore of the freon, we stopped, with still no cold air. the compressor seems to be trying to kick on and then stops repeatedly. Easy answer?
Elisabeth, The way I would approach your problem from where your at Now is. The freon that’s in there needs to be recovered. Then vacuum needs to be applied to the system for about 30 min. This removes air and moisture that may be causing problems. Then the exact charge required can be installed. Next the system can be leak checked and diagnosed as needed.
I recently had 120k service done on my 03 Lexus LS430. The next day the the dash vents stop releaseing air yet I could hear the blower was running on high. This problem went away only to re-occur he next day.
Just a few days later while driving to work the air con stopped cooling for about 10 minutes then it began working again. This happen several times since and now it seems to cool only for very short periods of time if it does at all.
The coincidence of these 2 problems along with the recent service makes me wonder if there is more to my problem than the compressor, which the repair service company has told me needs to be replaced.
Joe : It sure does seem like a strange coincidence and you do have good reason to be cautious. As a mechanic there are 2 words I try to steer clear from “Always” and “Never”. Because of that one automobile out there that can through you a complete curve ball!
Hi, I have a 2005 Jeep Liberty; ac has been working sporidically (meaning it runs some days, some days it does not). I have put the guages to it and the low side is very high and high side is low. What are your initial thoughts based on this? At first I thought maybe a clog but then it shouldn’t work on the other days no?
I am leaning towards a compressor going bad or maybe a clog or even both. Sometimes material from the compressor can cause clogs in the system. Clogs can shift and move and cause intermittent operation.
Here’s a strange issue:
My compressor had seized on my 2000 Town Car and broke the belt. The compressor and the belt were replaced. The air runs perfectly cold. however, it seems as if the system is always on. The high-pressure side from the compressor to the can gets completely frozen even when the A/C is not turned on. When it is, it freezes up after about 20 minutes and no air comes out from the vents. 15 minutes of the car turned off and melts and blows fine until it freezes up again. Also, there is no clicking from the compressor AT ALL, even when turned on.
No one seems to be able to figure this one out. One mechanic told me it seems to be always on. What are the dangers to the system if this were to continue?
HELP!!
Help!!!
Richard: 2 things come to mind. First the compressor always being on. If the air gap between the clutch and compressor pulley is not correct you may not get disengagement when it is turned off. This would also account for the no clicking situation. The air gap may need to be adjusted on the replacement compressor. The air gap is simply the space between the compressor clutch and compressor pulley with the vehicle off.
The freeze up issue. When a compressor seizes it usually spreads tiny pieces of metal throughout the system. It is always recommended to flush the system before replacing the compressor. Maybe a tiny piece of the old compressor got stuck in the expansion valve? This would not allow the system to respond to the freeze up by controlling pressures.
it seems like the pulley on the a/c compressor keeps seizing up and making the belt rub when the car is idling then will go again and seize up again. any ideas what this is. the car is a 2005 jeep liberty sport 6 cylinder 4×4. thanks