Red gets constant fused power, black is ground, dark green goes to the compressor and light green goes to the PCM.

Which pin from the Green / Blue LS 03-07 LS PCM would connect to the factory G Body AC box harness? LS PCM C2 Green connector Pin 43 A/C Compressor Clutch Relay Control (A/C)?

 

AC Compressor Clutch Relay Control Wire from the LS PCM, any of them, is the wire from the PCM that is the ground to the AC Clutch Relay in the Fuse/Relay Box under the Hood. When energized it engages the Clutch and the AC Compressor starts spinning.

The older cars without the PCM controlling them used the pressure switches. Dark Green wire there is going to the factory AC Compressor in the Gbody, there's a Connector on it with that dark green wire and a black wire which is the ground. It's been a while since I've seen the older stuff but there's an AC Relay as well, just not controlled by a PCM.

 

Reading the factory service manual, it appears the AC Control head under Max or Norm send 12V through the light green wire to a AC Cutout relay. The ECM would provide ground to this cutout relay which is what you stated. However where would the ECM take a signal to know the AC has been requested to turn on fans, bump up idle, etc?

I do not have the AC clutch relay or cutout relay under hood, and I am assuming this is needed?

This video explains it differently, they state that the light green wire goes to the AC recognition on the LS PCM to bump up idle when the AC is on.

 

To the first part that is all right there in that Schematic, just hard to see but it's there. Lime green wire is what's coming out of the AC Switch on the HVAC Controls in the Dash. It's fed by the 25A fused brown wire. Turn it on to any of the AC settings or the Defrost that lime green wire is 12v hot going out to the AC Relay and the ECM. ECM gets that 12v which is saying the AC is switched on, it grounds the AC Relay allowing it to energize and turn on the AC Compressor Clutch.

So that's how it works, hard to see but it's there and if you know how to read a Schematic.

You can keep the Gbody AC Relay or wire in one on your own in a Fuse Box for the LS Engine, your call on that one. Both would do the same you'd just have to properly wire the AC Compressor Relay Control wire to the Gbody one from the LS PCM if you wanted to keep it.

That lime green wire off the Gbody AC Switch is 12v when you turn the AC on and you can take that lime green wire directly to the AC Request Signal Pin in the LS PCM. Even in the LS PCM when it sees 12v on that wire it bumps up the Idle, turns on the Fans, and grounds the AC Compressor Clutch Relay so the Compressor starts spinning. So that video is correct.

So basically if you want it simpler and you have the AC Pressure Switches going to the LS PCM, I'd have the whole thing ran by the LS PCM and just the lime green wire from the AC Switch in the Dash going to the LS PCM. Seen many people do it that way it works fine. Fuse box under the Hood with all the LS Engine Fuses & Relay in it, wired correct and clean. That's how I'd do it.

I think I explained it well enough.

 

OK thanks for your explanation.
So the PCM needs two wires connected:
Pin 17 on the C2 connector for AC request (12v from the light green wire from HVAC controls)
Pin 43 on the C2 connector for A/C Clutch Relay Control (ground from PCM to an AC relay)

Unfortunately on the later 2003 to 2007 Blue Green PCM's (except for a specific few), do not have a 12v analog AC request so unless I modify the PCM circuitry following steps here, it won't work for me: https://ls1tech.com/forums/conversio...c-request.html

You Tube

I am going to have to figure out how to wire up a low pressure switch and a relay to control the AC clutch. I won't be able to manage fans and idle with the AC control.

 

Sounds like you need to simplify it and go to a Red/Blue 0411 PCM, Drive by Cable too.

AC Clutch Relay is simple, it's literally in that Schematic you posted. Four posts on it, two of them are the same wire that's the 12V into it.

 

https://ls1tech.com/forums/conversio...c-request.html

 

Are you running a 2007 van PCM service number 12602801 If you are it has the IAC drivers and analog A/C request

 

OS is 12613248 which I do not believe has the analog A/C request.