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compressor won't engage

s102000driver48 on Sun April 17, 2011 6:11 PM User is offline

Year: 2000
Make: chevrolet
Model: s-10
Engine Size: 4.3
Refrigerant Type: r134
Country of Origin: United States

Have a problem with my S-10 that is baffling me. I turn the a/c control in the cab to a/c or defrost, but can not get the compressor clutch to engage. I have replaced the high pressure switch that is on the side of the accumulator , but still nothing !!!!!! Next I checked all the fuses that were marked A/C to rule out a blown fuse. Everything looked good there that I could find. After that I jumped across the two connections that were in the connector that fits on the high pressure switch. When I did this the compressor clutch kicked in. I even unscrewed the new valve and pressed in on the tip of the schrader valve thinking maybe it was stuck. Everything seemed normal there. There is a box under the hood that has more fuses and relays. I checked the fuses, but did not check the one relay marked a/c. Is there a way to check that relay ? Can anyone think of anything else that I might have over looked ? Weather is starting to get warmer here in Illinois and want to get this fixed before hot weather sets in. Thanks


TRB on Sun April 17, 2011 7:02 PM User is offlineView users profile

How much refrigerant is in the system?


When considering your next auto A/C purchase, please consider the site that supports you:

GM Tech on Sun April 17, 2011 7:52 PM User is offline

Number one failure mode of mobile a/c systems is loss of refrigerant- the "high" pressure switch you jumpered out is actually a low pressure switch- which you have proven is what is keeping the compressor from running. It won't trigger compressor on until system pressure reaches 47 psi- so what is your system static pressure? From here, I'd say it is less than 47 psi and if it is warmer than 50 degrees out when you tested this, then I'd say you have about 4 ounces of refrigerant in your 30 oounce system-- That would be about 10% of what is needed to adequately cool your truck.

The switch is most likely doing its job (gage set with system pressure will confirm). The switch is keeping the compressor from running with little or no refrigerant in the system. This will protect your compressor from burning up due to lack of lubrication.

Number one leak location is under belly of HT-6 compressor- is yours oily/greasy?

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

s102000driver48 on Thu April 21, 2011 11:12 PM User is offline

s102000driver48 on Thu April 21, 2011 11:24 PM User is offline

Thanks GM TECH for replying back to me. I am an shade tree mechanic ,but know very little about A/C. I have a friend that runs an autobody here in town and one of his employees does A/C work. I will try and tackle the simple fixes ,but don't have the tools or the gauges for this fix. I think it is better off left to a professional. To answer your question, under the compressor was completely dry. I replaced the compressor two years ago with a junk yard one out of a 2001 ( old one locked up ). Vehicle has 234000 mile on it and is 11 years old so I not going to put a lot of money in it. But thanks again for pointing me in the right direction.


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