A/C Not Working - Electrical Issue?

snoreidiocy · Oct 22, 2025

Just bought a 03 Sierra 1500 Quadrasteer a couple months ago and I have a weird issue with the A/C (apparently it hasn't worked for a really long time, previous owner just didn't bother fixing it since he didn't live in a hot area). Replaced compressor, condenser, accumulator, basically everything in the system. What I noticed is something isn't telling the compressor to kick on. I can turn it on/off manually with a scanner and everything will work great. Tried replacing the low-pressure switch, did not fix issue. No codes were shown for the A/C system but still decided to clear all codes. Got great cold air for a while and compressor was cycling properly. This was until I decided to set the temp on auto (truck has the digital thermostat). Compressor never turned back on even when setting the A/C back to manual. Could it be the HVAC module has gone bad? I've also heard of the cabin ambient temperature sensor (part # 22834330) going bad on these trucks, thinking that could also be an issue here but want to get more input before I throw any more parts at the truck.

Any input is greatly appreciated. Thanks!

Tonimus · Oct 22, 2025

First, welcome to the forum. Have you tried re-setting to manual and re-clearing the codes to see if you can replicate the "fix"?

ORVietVet · Oct 23, 2025

Welcome to the forum from Oregon.

There is a couple reset procedures floating around on you tube that you can try. BUT, I had a recent driveway customer with a problem that was the auto a/c worked intermittently and we did a reset and it would then work fine for 2-3 days and then right back to the same problem. Replaced the control head and did the relearn/reset and has worked fine ever since.

AuroraGirl · Oct 23, 2025

snoreidiocy · Oct 24, 2025

I haven't tried re-clearing the codes or manually turning the compressor on with the scanner again since I don't have easy access to a scanner at the moment. I also tried resetting the HVAC control head a few times like ORVietViet suggested and that didn't work either.

I verified the low-pressure switch is working fine, and the AC COMP fuse isn't blown either. At this point, I'm thinking it's either a wiring issue or the HVAC control head is bad. Will take a further look at some of the wiring just to verify and if I can't find anything, then I'll order a control head from eBay and see what happens.

Thanks for the help and for the warm welcome!

AuroraGirl · Oct 24, 2025

snoreidiocy said:
I haven't tried re-clearing the codes or manually turning the compressor on with the scanner again since I don't have easy access to a scanner at the moment. I also tried resetting the HVAC control head a few times like ORVietViet suggested and that didn't work either.

I verified the low-pressure switch is working fine, and the AC COMP fuse isn't blown either. At this point, I'm thinking it's either a wiring issue or the HVAC control head is bad. Will take a further look at some of the wiring just to verify and if I can't find anything, then I'll order a control head from eBay and see what happens.

Thanks for the help and for the warm welcome!

You need a scan tool.it will literally tell you why ac is inhibited directly
Also, the tsb I posted was very specific about what switch is used. Did you verify the part number cross or original part number