I have put a 12v cummins in a 2003 ram 1500 gasser chassis. truck is running/driving but i'm having problems making the a/c work. I'm using a 2nd gen compressor, which plugged straight into the 3rd gen gasser connector and the gasser pressure switch is installed and wired in. now, after vaccing down the system and charging it, i cannot get the compressor to cycle and condenser fan to kick on. i'm assuming its ECM related as I had to run a ground to the compressor relay in order to make it cycle manually.

just looking for some ideas/insight from others that have put a 12v in ECM controlled trucks and what y'all did to make the AC work. cheers!

 

The gasser likely doesn't know the engine is running.

Do you have the ESS sensor hooked up and your dash tach working?