A/C not working

treasures4u1 · May 3, 2015

OK, this is my last hope. Summer is here. The a/c compressor went out in our 1995 C2500 Extcab Sierra pickup, 5.7L 350. We replaced the compressor, accumulator, condenser, hoses, o-rings, orifice tube, and the climate control. We have spent a lot of money and have been through hell with this thing. Well, the clutch is not turning on the brand new compressor!!! What the heck? Any help? PLEASE!!!

1997SierraSLT · May 3, 2015

The first thing to check is if the compressor is getting voltage. My climate control switch unit in the dash is notorious for cutting in/out.

Lazarus Long · May 8, 2015

If the mechanicals have all been replaced with known good parts, it could be the control module. The module in my 97 is going bad, it now only has medium-high and off. It still works good enough so I haven't fixed it.

sahls01gmc · May 8, 2015

The clutch will not engage if it does not have enough freon in the system. Have you verified proper levels? Sounds like you are close, might take a 10 minute diagnosis from an AC Tech.

treasures4u1 · May 10, 2015

TY everyone for all your advice. But we replaced the control module and we checked the refrigerant.

chevy529 · May 10, 2015

If you have checked or replaced all mechanicals (with new parts) and refrigerant. The only thing left IS power.

bronyaur · May 11, 2015

If you have checked or replaced all mechanicals (with new parts) and refrigerant. The only thing left IS power.

Agreed. I am no AC expert, but I've fixed three of these systems by replacing the low pressure cut-off switch on the accumulator. Pull the connector and jump the contacts with a wire. If the clutch engages, check your pressures with manifold gauges. If the numbers are good, replace the switch. If the refrigerant is low, there's your problem. Check for leaks and re-charge.

If you pull the connector and jump it with a wire and the clutch doesn't engage, you have a power issue.

barry G · May 15, 2015

I am getting a 96 going again. for those years something called a "thermocoupler" on brand new compressors might not be going right.

that goes on into 2003 apparently. Hit or miss.

if you still have your old compressor, could swap stuff around onto the new one.

you did not mention high side or low side valve. sometimes those pee a little leak to full drain.

00Silverado4x4 · May 18, 2015

After replacing all those parts did you have the system evacuated prior to refilling with refrigerant? If not you are going to have a lot of air in the system and that will wreck havoc on the system.