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AC Troubleshooting Procedure

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AC Troubleshooting Procedure

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Old 05-22-2007, 11:43 AM
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AC Troubleshooting Procedure

My 92 Camaro RS had an AC that got so cold you had to turn it down or freeze your hands to the steering wheel. Then, it seems to have suddenly quit cooling so now to trouble shoot it.. I have been looking through the posts but haven't been able to find a good step by step troubleshooting procedure that starts from the basic least invasive, least expensive checks then to the big bucks take it to the shop issues.. Anybody have one..??..
Thanks....
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Old 05-22-2007, 12:18 PM
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Re: AC Troubleshooting Procedure

Honestly unless you already have experience or knowledge of AC system and the right equipment to do it, you are better off either rolling down the windows or taking it to somewhere for repair. If you haven't upgraded to R134A, repair on a R12 system is very pricey if you can get it. The EPA has required certification since 96 just to purchase R12. It has nothing to do with yours or anyones skills or knowledge purely legalities. If you can find R12 you could expect to pay $20-25 for a 12oz can, maybe more, these systems can take IIRC 3-4 LBS for a full charge.

You most likely have a leak, which would require recovering the R12 remaining prior to repairs. Even an electrical problem most cases require recovery also. Any way you go towards repairing or upgrading to R134A will be expensive.
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Old 05-24-2007, 12:50 PM
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Re: AC Troubleshooting Procedure

I have looked through many of the threads and am trying to piece together something like a procedure lacking any real procedure. So here's the deal. I like to make sure I know what the problem really is or at least be very close to it before taking it to a shop. There are too many less than forthright shops out in the world. Additionally, some things I might be able to change or fix and then have it finished up by taking it to a shop. That might save me a few to a lot of bucks (ex, change a fuse, change a switch, change a relay, change a connector, change a wire, change a hose, change a compressor, etc. depending upon what a diagnosis says). But, to do that, a good step by step procedure and system diagram would really help. I am an engineer and have worked around Freon in the past with electronics so know all of the precautions for working with it. So, that is why I was looking for a procedure that I could at least work partially through before reaching a point where the shop becomes necessary. Doesn't sound like anyone has such a thing on here so I will go ahead with piecing information together to see what I can come up with... Just was hoping to save some time if one already existed..

Thanks for checking the thread......
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Old 06-07-2007, 09:42 AM
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Re: AC Troubleshooting Procedure

I had a nice little write up going on my progress and the forum had me sign in again and I lost it. Soooo, here is a quick condensed version of my troubleshooting the electrical side.

The Compressor Clutch is controlled by the ECM through a relay. One side of the relay coil goes to 12v through a fuse the other side is pulled to ground by the ECM when it wants to engage the clutch. Check the fuse, check the relay, check the compressor clutch if the clutch is not engaging and the compressor is not starting after verifying that the relay is working.

The ECM is told that it is ok to run the compressor by the low pressure switch on the accumulator. If the switch is open the compressor is off (clutch disengaged). If the switch is closed the compressor is turned on. Jumper across the low pressure switch and the ECM should turn on the compressor by turning on the compressor clutch relay. Do that only briefly to prevent damage to the compressor. When the switch is working properly, the compressor should cycle on and off as it cools. If jumpering the switch didn't turn on the compressor and you already checked the relay side, the ECM could be bad or there may be a wiring problem.

I think the ECM is told to turn off the compressor if the high side pressure gets to high via the high pressure switch in much the same manner as the low pressure switch. I haven't gotten to this one yet.

A cycling compressor every few seconds is supposed to relate to low freon pressure and, therefore, needs charging.

Please note: This is what I did in testing and I am a novice, not an authority on this. Use the information at your own risk.
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Old 06-07-2007, 09:54 AM
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Re: AC Troubleshooting Procedure

Larry is pretty close. If your compressor is cycling(i'd say visual check of this is the first part of procedure), I'd check for pressure in the system.

If the compressor ain't cycling, you may be out of refrigerant. --->Compressor won't turn on without enough pressure to trip the switches.<---

You can put a tire gauge on the schrader valve to measure your system pressure. Read the rest of the post before doing so, though, as a sudden release of refridgerant out the wrong valve will freeze your finger/hand into SOLID ICE in less than a second.. It's even worse than it sounds. Have you ever seen a picture of really bad frostbite?

Regardless, I wear gloves whenever I'm working on a charged A/C. Not those "mechanix" gloves, but nice, thick, work gloves.

Do this on the LOW SIDE ONLY. This is the valve on the accumulator(the big silver cylinder that has two fittings at the top). I would run the car for a bit with the A/C "on" to make sure to get a good reading. Anywhere below 30psi on the low side is too little...above 45 or 50psi and you have other issues(R12 specs, not R134).

The HIGH SIDE VALVE is the shrader valve on the tiny line laying on the "frame". More or less under the accumulator. DO NOT TOUCH THIS!!! Unless your a well trained A/C tech. High pressure side issues are usually either the "high-pressure switch" or blockage at the orifice tube.

However, I would eliminate EVERYTHING ELSE before assuming a problem in the high pressure side of the system, cause at the very least your gonna need to evac and refill, most likely a new compressor and/or other parts.

If your pressure turn out okay, you should then try the electrical steps outlined by LarryD above.

Last edited by pizza_guy; 06-07-2007 at 10:14 AM.
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Old 05-06-2008, 02:24 PM
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Re: AC Troubleshooting Procedure

so what happens if you put 134 in instead of r12? will it still cool?
and how do you "convert" it to take 134?

I recently charged my 92 trans am and got it cold, but now a few weeks later the ac is not blowing cold again. My compressor was cycling on and off when it had coolant...I' guessing a leak...anyone know the most common areas to look for the leak? Does anyone have experience with the black light dye that can be put in the system to look for leaks? Any help would be appreciated.
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Old 05-06-2008, 08:33 PM
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Re: AC Troubleshooting Procedure

If you put in R134 instead of R12, you run into problems with incompatibility of the oils in the system probably resulting in compressor burn out and/or sludge... You need to fully flush the system if you are going to R134 and change the compressor oil in it... I got myself certified and went to R406a in my Camaro and I get 32 degrees at the vent...
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Old 03-29-2016, 06:44 PM
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Re: AC Troubleshooting Procedure

LarryD where is the ac relay located?
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Old 03-29-2016, 07:00 PM
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Re: AC Troubleshooting Procedure

Hi guys. No offense to any posters but the biggest difference is the connectors. r12 and 134a are compatible. Ran it in my own systems for years and even mixed them together. The pag oil is not incompatible at all. I've repaired hundreds of systems and "converted" many many of them. The conversion is mostly just adding adapters to the lines and sticker to say its been converted. They spead that to sell conversion kits. The prosedure to fill and repair the systems is virtually the same.

al
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