Air conditioner signal integration

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
http://i189.photobucket.com/albums/z...ruckwithAC.jpg

Compressor And Bracket
http://i189.photobucket.com/albums/z...Compressor.jpg

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.

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

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.

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.

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

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.

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

Thanks for the responses guys...

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

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.

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?

That's the way the F car system works and Greg and I were at one time trying to perfect this hot wire job. Maybe he'll chime in. I forgot where we were with his (he runs the 2002 Camaro PCM that works more like what you're talking about).

As far as the 2004 PCM, it's not voltage but an actual Class2 message from the HVAC to the PCM requesting AC meaning you'll have to use the 2004 AC control to make it work like stock.

Ohhh...I gotcha...well, I guess I'll get to digging around some more and reading the GM Service Info on the AC to see if there is someway to make it happen.

Thanks again for the input!

Cody B.

I haven't got around to doing mine yet, been way busy with other distractions and just being lazy on other day vegging out on here. I'll post up when I get some real results.

Yea, I hear you on the way too busy part. Been working on finishing up a 5.3 into an 1981 Jeep CJ...we should start it up tomorrow and then its back to my car...

But given its close to winter coming up, I figure I'll let the minor AC nuances slide till oh...next June :)

THanks for the help though guys,

Cody B.

I'll have to dig, but the 2004 controller can take a discreet input instead of a class II message. Talk to some of the better tuners out there, they may know how set it up. It most likely needs a pin to the PCM that is not in the regular diagrams.

Look through the service info for a 2003-2004 Van vs. a Sierra. They use the same controller, same software, but depending on which pin you use, and likely some different cal values...

This is the Sierra.. on the blue connector

Pin Wire Color Circuit No. Function

14 RED/BLK 380 A/C Refrigerant Pressure Sensor Signal (A/C)
43 DK GRN/ WHT 459 A/C Compressor Clutch Relay Control (A/C)
80 BLK 2751 Low Reference (A/C)


On the savana, blue connector.
17 DK GRN/WHT 2523 A/C Request Signal (C60)

43 DK GRN/WHT 459 A/C Compressor Clutch Relay Control (C60)

55 DK GRN 603 A/C Low Pressure Switch Signal (C60)



If you poke through the service manuals, and look at the schematics.. I think you'll figure out a solution. I'll bet one is ClassII (Sierra), one is a hardwired (aka discrete) input on the van..

Did you ever figure this out? My engine and PCM is an 06. I have the A/C hooked up and working in my 85 on just the truck's controls, and it works fine. But if I could figure out how to tie it into the PCM I probably would.

There isn't a way to do it currently on the 03+ PCMs. I have been after HPtuners to look into a way to switch the AC signal from Serial to switched, but no dice yet.

Red, did you ever figure out how to do it on yours?

Nope, was running a Sanden compressor so I just triggered it from the 93 signal wire to the clutch and it stayed on all the time, no cycling. The coils would freeze up from time to time and I'd have to turn the a/c off so the fan could thaw it out.

Well that sucks. Seems like if it was engaged all the time it would put a load on the motor all the time?

Quote:

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Originally Posted by RedHeartbeat

Nope, was running a Sanden compressor so I just triggered it from the 93 signal wire to the clutch and it stayed on all the time, no cycling. The coils would freeze up from time to time and I'd have to turn the a/c off so the fan could thaw it out.

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Red, don't you mean, you just had it triggered from the accumalator pressure switch wire, via the A/C request relay?

I don't have that switch anymore. I had a trinary switch installed in the high pressure side. The green wire that used to go to the accumulator switch now goes to the trinary switch and then to the clutch. :thumb:

i know this is an old thread but im in the same boat right now. ive got the fans wired for low/high and pcm is tuned for it and im ready to get the lines fabbed up for the compressor but if there is no way to controll the fans/idle using a regular 12v signal instead of the class 2, then i might as well scrap this plan and just do something else... which will be uneccesarily expensive!!!

i know i can get the fans to kick on high bypassing the computer with a few wires and a diode if i have to. but im concerned about the idle. how bad is it when the compressor is engaged? does it want to stall out? has a solution been figured out yet?

Sub'd

I looking for this fix to help out in any way I can for those looking for it.

I found a post on ls1tech about it. Seems like it can be fixed in a tune. As mentioned above, HPTuners doesnt have anything yet.

http://ls1tech.com/forums/pcm-diagno...ntrol-pcm.html

Quote:

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Stock PCM has full control over the A/C compressor.
To enable a standar 12V signal for the A/C request (instead of class 2) you need to change it with Tunercats or Jet DST. HPTuners currently doesn't have access to change it.
There are more parameters to be modified, but id works good. I have installed a few swaps with A/C and no problems. You just need to make sure wiring is correct and PCM tune is also correct for the compressor type you have (fixed or variable displacement). You'll need the low and high pressure sensors depending on the setup

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dude thats exactly what i was looking for. thats great news!! i talked to another member on here who is saying his is idling just fine not hooked to the new pcm. so im going to try that first and see how it goes. if i have issues, then it looks like i will be looking for a tuner who uses that software... there is a local tuner with dyno that i plan on going to once i get the turbo on, hopefully he uses that software... well see. but thanks again for that find!! i looked everywhere. i dont know how i missed that over on their sight. awesome

I was finalizing up my wiring on my 90 and have the same question. Mine isnt running yet so I dont know what it will and wont do.
I know I cant tie in a 12+ hot to activate the ac idle up when the compressor kicks in directly to the ecm, but I can wire something up for the electric fans to kick into high speed.
Most posts I see say the engine will sense the load and automatically idle up. What I am unclear of is the ecm tuning.
I see most guys running cable driven (dbc) tb where I am running a dbw tb. Is that where the discrepancy is? Are dbw ecms able to idle up where dbc ecm tunes won't? Anyone have any insight?