Vintage Air with LS Swap - non-pcm control strategy

[ls1nova71]

Originally Posted by NC_John

Its an 04 truck pcm, blue/green. I know the pcm has the output but don't know if it works when the AC is controlled externally (like through VA). If the output is in the pcm for high rpm/wot cutoff, but the AC command is actually triggered by the bcm, does the pcm disable output work regardless of whether or not AC is on? If so, that would work. Need to figure that out.

The A/C isn't controlled by the BCM in an '04. It's controlled by the HVAC switch, which is a module that communicates with the PCM via the serial data line, hence, there is no dedicated 12v A/C request wire. You can kind of get around it though, but it's not perfect. What you can do is find a blue/green PCM that has IAC drivers in it, add the 12v request wire, then have the tune changed to make it work. If I remember correctly, you need to change it from serial request to analog cycling. This would allow you to control the compressor through the PCM. What it wont do though is run the electric fans, you will need the VA trinary switch for that. What is the service number on your PCM? I'm going to make a wild guess that its 12586242, but if it's 12586243 then that's the PCM you want. There are others that will work, but these are specifically 2004's.