How to tune for AC load, when I do not have AC connected to PCM

[TXjeepTJ]

Chevelle New Idle 8-12.hptI have a 1970 with a swapped in LQ4, decent cam 232/240 .595/.608 on 115

I had it idling good for the past 2 years with the tune I had. I just now installed air conditioning, and since it is in a 1970 Chevelle I do not have the AC connected to the PCM to tell the PCM that the AC is on.

I went through the "how to tune idle" thread and did everything in there, but every time I put it in gear w/ the AC on it idles really rough. I've increased the base idle airflow table in gear and that helped, but when I go to drive it and I come to a stop - it wants to die and starts idling rough/or dies.

Where else can I look? Using the scanner I set the timing to a constant 23 degrees to see if timing was the issue causing the stalling, but the same thing happened.

[RandomEnthusiast]

First off I would change it to not fitted for the a/c under system a/c tab. Or spend half an hour and wire in a a/c compressor on signal and change it to analog. I had an issue with my a/c on wire on my 93 and it does the same crap until you fix it. It would idle down to 400 or so.

[TXjeepTJ]

First off I would change it to not fitted for the a/c under system a/c tab. Or spend half an hour and wire in a a/c compressor on signal and change it to analog. I had an issue with my a/c on wire on my 93 and it does the same crap until you fix it. It would idle down to 400 or so.

Do you know which pin on the PCM tells the PCM that the compressor is on? Everywhere I look it just talks about how to wire EVERYTHING up, like the pressure sensors to have the PCM control the compressor- I just want the PCM to know that the compressor is on so T will raise the idle etc

[RandomEnthusiast]

I can't remember off the top of my head if its 12 volts or ground. What year and what model is the pcm out of. I'll see if I can find a diagram.

[TXjeepTJ]

Thanks for the reply - I have a 2005 PCM w/ the Green/blue connectors - off of a 2005 Silverado 2500

[TXjeepTJ]

I can't remember off the top of my head if its 12 volts or ground. What year and what model is the pcm out of. I'll see if I can find a diagram.

I found that:
Pin 14 is AC refrigerant pressure switch
Pin 43 is AC compressor clutch relay control
Pin 80 is AC low reference

I'm wondering if I change my AC compressor to "analog" in hptuners and then apply 12volt to 43 when the compressor is on, if that will trigger the pcm to bump up the idle rpm/increase idle air flow