99 GMC C2500 AC problem - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-08-2012, 04:27 PM   #1
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Default 99 GMC C2500 AC problem

I would like to see if I can get some help with an AC problem. The compressor clutch is not engaging. I have checked both fuses in the fuse box. I have pulled the relay and swapped with another one. I have jumpered the low pressure switch. I then took the relay apart and physically closed it and the clutch pulls in. Question... Should there be 12 volts at the low pressure switch on this model?
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Old 06-08-2012, 04:40 PM   #2
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I can't answer the questions you are asking. But do want to mention I had the same problem with my 2001 Bonneville A/C clutch not engaging. I checked the fuses and relays. All good.

I then read a post that low freon can prevent the clutch from engaing. I purchased a freon fill canister with attached gauge. It reported empty. I filled the system with freon, and my A/C clutch started to work and has worked fine for the past 45 days.
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Old 06-08-2012, 04:44 PM   #3
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X2 to the previous response. Check freon pressure.
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Old 06-08-2012, 04:44 PM   #4
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Thanks for the reply... I did not mention that the compressor was replaced last month and I did jumper the low pressure switch to check for low freon.
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Old 06-08-2012, 10:59 PM   #5
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Possible you might have jumped the high side switch?

Another question. Who replaced the compressor? Was the system put back in service per the service manual? If a shop replaced it and recharged the system with PAG oil and R134, then I would go back to the shop and have them fix it.
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Old 06-08-2012, 11:10 PM   #6
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The switch I jumpered was on the side of the accumulator on the firewall. The compressor was replaced by a shop in town. In fact this is the third compressor. They have had a hell of a time. This AC stuff has not been fun. The first compressor destroyed itself. The second just froze up. They changed from GM oil to oil from BG this last time. The compressor runs when I manually engage the relay. Oh well it is going back to them Monday.
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Old 06-08-2012, 11:13 PM   #7
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Good idea. Take it back to them so they can fix it.
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