Hi Scotty, have a 1996 GMC Sierra z71 with just over 100,000 miles. My AC condenser will not engage and my AC blows hot air. I have: replaced the condenser, checked the charge it is not over charged either, replaced both sensors, have leak tested the system, replaced the resistor, checked all fuses and electrical for current, jump started the system by bypassing the relay under the hood- which worked initially so I replaced the relay but that also didn't work, and I am at my wits end! Please help! Thanks so much in advance, God bless! Also, the truck has no codes.
There wouldn't be any OBD2 codes for the HVAC system.
If the AC works when you bypass the relay then it's mechanically OK and you have an electrical problem. It needs to be diagnosed with a bidirectional scan tool (Tech2 or equivalent for that vintage GM).
