Air conditioner signal integration

[93blackbeast]

Hey AC Guru's,

I've recently installed my AC with the Kwik Performance setup and have hooked my compressor up through the original AC compressor wires coming from the low pressure switch. My truck is a 1993 as most of you know, but thats just a reminder. Here's a pic of the setup, minus lines (haven't gotten an updated one yet).

Complete Setup


Compressor And Bracket


I'm wondering how I can communicate to the new PCM controlling the LS1 that I have my Air Conditioning on.

The setup works okay now, but I have no control on when the second fans come on or how the RPM's should come up a little to compensate for the additional load on the engine and would like to get this working properly.

The truck runs fine now, but I'm a stickler for making things right like they should be. I'm imagining that it will be tapping into a wire coming off the PCM with a 5v signal or something, but I'm just guessing there...

Thanks in advance,

Cody B.

[RedHeartbeat]

What year PCM/tune are you using to control the engine?

[93blackbeast]

I'm using the PCM out of an 04' Avalanche. It was the PCM I had running my 5.3 when it was in the truck and I just tuned it to run the LS1 from that.

[RedHeartbeat]

Maybe GasGuzzler can get you the PCM wiring for the A/C. I have it for the 2002 Camaro but its most likely different on your engine/pcm combination.

[LS1GMCTruck]

'04 & up is serial-data controlled A/C correct? Always wondered how that works, lol.

[93blackbeast]

I have the PCM Wiring for the setup, but I just don't know what I need to do.

On the Green PCM Connector

Pin 14 is the A/C Pressure Signal
Pin 15 is the charge indicator control (I don't know if this is volts or freon)
Pin 43 is the A/C compressor clutch relay signal

I'm guessing its one of those, but I'm not certain. The blue connector didn't have any A/C related things on it that I could see.

Thanks again guys,

Cody B.

[GasGuzzler]

03+ uses ClassII HVACM so you'll have to manually generate and/our cheat the system.

[93blackbeast]

Thanks for the responses guys...

SO GG, whats the easiest way to cheat the system without frying a PCM in the process

[GasGuzzler]

After looking at the schematic I'd say you should control it like the truck was designed and not with the 2004 PCM since this system requires a ClassII request from the HVAC controls to the PCM then the PCM grounds the compressor relay. The only downfall is idle with and without the AC on. This is something we're dealing with on RedHeartbeat's truck too although his has a more simple OS.

[93blackbeast]

Thanks GG. That's how I have it working now, using the controls that came off of the 1993 to signal the AC clutch to engage.

I was just wondering if there was a way I could use that 12v signal that i send to the clutch to maybe go through a resistor and then tap into a PCM wire that would let the PCM know that the AC is "ON". That way, it could adjust the idle and such as if it were controlling the AC. I still want to control the AC through the trucks controlls, but just like you said, fake the system out.

Does that sound like that would work at all?