Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
My AC relay won’t kick on. I don’t have control out put from PCM to my relay. My pressure and Freon levels are good. I jump pin 30 to 87 at the relay and compressor turn on and I have cool air inside truck. 04 Silverado. I check my low and high pressure switch and they are good. I don’t have a scanner to check input to my HVAC control module.
Pressure and sensors are good. I jump 30 to 87 on relay and compressor turn on and cool down. I check low pressure sensor it good and high pressure sensor and it’s good. How do I test the class 2 ser data wire coming out off ac control module to PCM to see if the pcm is get the correct inputs? I recently change the ac module with a use one but did not work. I still suspect a bad module AC. Any help thsnks
I don’t have a scan tool to view that data. What are my inputs in order for the PCM to ground my wire to the relay.? Is it only my low and high pressure sensors inputs? According to wire diagram ac control module get input signal from low pressure switch and PCM get a input signal from the high pressure switch. Question if the line class 2 ser data to the PCM is not communicating will that not command the PCM to ground my relay? Is that a input or just Communication between AC module and power control module. Back in the days we use to jump the low pressure switch and will activate the relay which turns on the compressor and we knew it was a bad switch or low on Freon. Not no more .
If the compressor command is over Class 2 there isn't much you can do without a scan tool. And even if it's hardwired you still really need the scan tool. The pressure switches aren't the only things that can inhibit compressor engagement on newer vehicles.
