Evaporator Fin Sensor Question

[PaulJohnson]

My a/c compressor is not getting power to it... . I have checked freon levels, replaced switch on the dash, replaced pressure switch down by the compressor. I do not know how to check the only thing left, the evap fin sensor. I remove the glove box door and see two small gauge wires coming from the HVAC box and I guess that is the evap sensor wires, can I jump those two wires and see if the compressor gets power then? I just can't figure out why 12v will not make it to my compressor. Sometimes I can reach over and turn on the a/c and it will work great blow cold but that is very rare, most of the time nothing happens but hot air. When the compressor actually gets power and turns on it is fine.

 

[sag2]

It's a thermister so just jumping it probably will not work. Don't know what year truck, but the compressor should be run by the TIPM based on commands and sensor inputs from the control head and the ECM. You really need to have a scan tool to see what the fin temp sensor is reading, and if the control head is telling the ECM and the TIPM to fire up the compressor. It could be control head, wiring, relay if it has one, ECM (unlikely) or TIPM. Scan tool will take the parts guessing out, and will probably be less expensive. And a generic engine code reader will not work, you need the dealer tool.