How to Troubleshoot my Chevy C3500 AC System


Asked by SCLB94 Jun 29, 2012 at 07:43 PM about the 2000 Chevrolet C/K 3500 Crew Cab Long Bed 4WD

Question type: Maintenance & Repair

Hi all,

I have a 2000 Chevy C3500.  I am having probelms with my AC.  I noticed the problem awhile back.  My compressor would not engage.  The AC system worked fine last summer and now that it is getting hot again I can not get it to come on.  I have already tested / done the following;
Jumpered relay to engage compressor - it does come on when I do this.
Add refrigerant to the system thinking it was the low pressure safety switch, this did not do anything and now I am afraid I have too much refrigerant and I may slug the compressor.  I have commercial / residential grade gauges but they do not fit on the auto style connections.  I need to get adaptors for this.
Checked the power across the relay coil - 12vdc and replaced the realy
checked the power at the cylinder (what I believe is the low pressure switch) 12vdc
checked the power at the compressor (connection on top) nothing unless I jumper the relay.
I tried to find a wiring diagram but I have not had any luck on the internet.

Any help you can offer will be great

2 Answers


Check to see if the electric fan at radiator is coming on when ac is turned on. It should run at all times while ac is in on position. If it not coming on ac will not engage. Hope this helps


Thanks for the suggestion. I looked at the fan and it is coming on. Any other ideas would be helpful and appreciated. Thanks

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