LS1 AC not being commanded by PCM

I did an ls1 conversion into my thirdgen camaro, and used a standalone PSI conversion harness with no AC provisions. Pocket - a member here and on thirdgen.org built a 4th gen harness to use on my car with the ls1 compressor, and connecting to my factory harness for AC, and pins on the computer (Red/Blue) that had to be added. It was plug and play but when I turn my ac on the compressor doesn't start, and I can manually jumper the relay and it kicks on. So I am thinking maybe its my tune setting?

I am using a pressure sensor for a 90 grand am three pin, as advised from thirdgen.org forum. ACDelco part 15-72104. It is wired correctly and using my multimeter, I am getting correct voltage on all the PCM's ac wiring. The only thing in question right now is the Red/Black wire on the pressure switch C2 pin 14, circuit 380. I register 4.2v there, and I believe that is too high for it to turn the compressor on. I don't know what the observable range should be for this?

I start the car with the AC turned on, and the fans immediately come on, but I don't hear the AC compressor engage. I have taken the pressure sensor pigtail loose, and the fans immediately go off, and I am almost sure I hear the AC compressor click like its either engaging or disengaging.

I have ordered another pressure sensor to see if maybe I have a bad one, I have read 2-2.5 volts is where it should operate. My ac tech that filled it with R134 swears it is filled correctly and the system shouldn't be over pressure.

I still have the third gen cycling switch hooked up, but from studying the 02 LS1 AC wiring diagram its not even being used. Should I unplug this?

The PCM was programmed with HP Tuners as an 02 Camaro OS ID 12212156

Any help or advice appreciated.

Bryan

I believe the pressure range on those sensors are 0-500psi. That would flow with 4.2v giving a "high pressure" reading thus disabling the compressor. Using HPT scanner, manually activate the ac compressor. If it activates that will confirm its wired correctly and you have an issue with the sensor or sensor wiring.

I'd remove the cycling switch, its not needed.

Josh

2 Attachment(s)

See attached, I can command it on manually through the scanner / VCM Controls.

All my issues were resolved by swapping the 5v and ground on the three pin connector for the high pressure sensor. Everything works as it should now. I am going to use an r134 switch on low pressure side so it will pass voltage through it from the ac switch. Just posting this for other folks future benefit in case anyone else runs into problems.