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Help with A/C Diagnosis (with video)

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shinzon

15+ Year Contributor
350
72
Sep 11, 2006
St. Petersburg, Florida
So I bought my '96 Talon eight years ago with a broken A/C, and with the recent wreck and probable total loss of my '97 daily driver DSM--just as oppressive Florida Summer begins, of course--I'm trying to diagnose and hopefully get the air in the '96 blowing cold again.

Same Symptoms have persisted throughout my ownership of the car: when I turn the blower on and hit the a/c button, the green light illuminates and stays steady, but the compressor clutch cycles between engaged and disengaged endlessly. At one time it'd blow cold(ish) despite the cycling, but these days it's like an angry drunk is breathing hot air on my face when I switch the a/c on. I also noticed that the green light didn't illuminate once or twice when hitting the compressor switch, a symptom that seems to have developed while the car was sitting these last years.

I tried bypassing the dual-pressure switch with no change in the symptoms; I tried replacing the a/c controller on the evaporator with one from a parts car with no change, nor when I jumped the connector terminals for the a/c controller. With no A/c controller attached, the compressor doesn't engage (obviously).

Here's a video of the compressor cycling:

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Any Ideas?
 
Last edited:
it doesn't sound good. Usually, the AC compressor will cycle when it's low on freon. Which means you have a leak somewhere. Have you tried adding a can or two of freon, and see if the compressor stays on. If you have to crack the AC system, you will need a vacuum pump to vacuum the system down, and let it set with gauges overnight to make sure there are no leaks. Then charge it up with freon and a can of oil. Or take it to an AC shop and let them figure out what the issue is. Good luck, and stay cool.
 
Thanks for the reply.

Wouldn't by-passing the dual-pressure switch allow the compressor to engage despite a high or low pressure condition? A friend suggested that the air-gap on the compressor clutch may be wrong, but I have little doubt that this is the original compressor, and one would think it was set correctly from the factory.

In any case, I borrowed a set of gauges last night, so I'll have more information about the system pressure later.

Edit: I'm reminded: many years ago I tried adding freon to the system and the gauge on the can seemed to suggest the system was over-pressurized. Does the compressor have some sort of internal protection against high-pressure conditions, one that doesn't rely on the dual-pressure switch?
 
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According to behrhellaservice.com "A defective or failing pressure switch can manifest itself as follows:
Insufficient cooling performance
Frequent switching on and off of the compressor clutch"

Sounds like the pressure switch is bad, especially since bypassing it yielded the same results.
 
According to behrhellaservice.com "A defective or failing pressure switch can manifest itself as follows:
Insufficient cooling performance
Frequent switching on and off of the compressor clutch"

Sounds like the pressure switch is bad, especially since bypassing it yielded the same results.
If the pressure switch was bad, it would work the clutch when it was bypassed.
 
So I bought my '96 Talon eight years ago with a broken A/C, and with the recent wreck and probable total loss of my '97 daily driver DSM--just as oppressive Florida Summer begins, of course--I'm trying to diagnose and hopefully get the air in the '96 blowing cold again.

Same Symptoms have persisted throughout my ownership of the car: when I turn the blower on and hit the a/c button, the green light illuminates and stays steady, but the compressor clutch cycles between engaged and disengaged endlessly. At one time it'd blow cold(ish) despite the cycling, but these days it's like an angry drunk is breathing hot air on my face when I switch the a/c on. I also noticed that the green light didn't illuminate once or twice when hitting the compressor switch, a symptom that seems to have developed while the car was sitting these last years.

I tried bypassing the dual-pressure switch with no change in the symptoms; I tried replacing the a/c controller on the evaporator with one from a parts car with no change, nor when I jumped the connector terminals for the a/c controller. With no A/c controller attached, the compressor doesn't engage (obviously).

Here's a video of the compressor cycling:

You must be logged in to view this image or video.

Any Ideas?
The problem could be the refrigerant temperature switch, which is located on the compressor itself. I had the same problem happen to me last year and it was this sensor.
 
The problem could be the refrigerant temperature switch, which is located on the compressor itself. I had the same problem happen to me last year and it was this sensor.

Thanks for the reply; I hadn't thought of that, and I'll check it out soon.

I changed out the timing belt on this car and I noticed a new symptom: as I as taking off the a/c bracket, my hand hit the compressor and I received a small shock (car was not running, obviously, and the key wasn't in the ignition).

What would cause the compressor to be electrified with the car off; some sort of short?
 
Also, you running R-12, or has it been converted to R-134A.

Small shock coming from the ground cable .. and you were in between and DC current found a direct path back to the battery.

. Could mean that you've got a bad ground somewhere (like bad battery connections or similar) .. and this could be your problem.

DC current runs from negative to positive - why the importance of solid and secure grounds. Plus why you disconnect the ground cable from the battery when working under the hood.

-DSM
 
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