kingb

on a 5.3 factory wire harness, what has to happen to engage the compressor, i think there are two wires.

patrick_rodgers

If it is like the LS1 setup (2000 Camaro), the computer gets +12V as ac request. The pressure sensor in the ac line has three wires (special ground, +5 volt reference in, and sensor output). If the refrigerant pressure is within limits, the computer signals the ac clutch relay to turn on and then there is a input to the computer to make sure clutch relay closed.

I used two micro switches (cooling and defrost) to close another relay, and then used the heater fan switch output to provide the +12 volt to the computer - Blower motor has to be turned on to get ac.

Right now, this is all theory, ac hook up will be this winter.

Jones'n

Actually, the 99-02 truck engines work differently than the LS1.
red 17 gets 12V requesting the A/C on
if red 55 is grounded, then red 42 supplies a ground to the relay to engage the clutch.
red 55 is supposed to go through a simple pressure switch that closes the circuit to ground when the pressure is okay in the system.

TXjeepTJ

iTrader: (8)

with the ls1 ac compressor in a wrangler, im using the jeeps pcm to controll gauges and ac, im also using jeeps ac lines

the ls1 compressor have a 2pin plug which im guessing is a + and - that engages the clutch on the compressor

the jeeps compressor only had 1 pin (a +) and the other side was grounded. to make the ls1 compressor clutch work do i just ground pin a(or b) and then run the jeeps + wire to the other pin?

idk much about electrical stuff

gagliano7

I have 12 volts going to a/c request when a/c is on but nothing happens (1999 gmc pcm). If i ground pin55 wil the pcm then work a/c idle control correctly? I know this is from an old thread. I have a 5.3 in a 1992 chevy pickup using trucks a/c system. A/C works fine i just want pcm to adjust idle when a/c is on.

Thanks Joe

bczee

iTrader: (12)

On my Chevelle, I use the stock Chevelle (green wire) to activate the compressor clutch directly and just grounded the other terminal... I am using the stock Chevelle AC system with just the LS1 compressor in place of the older pump.

May not be the best way, but it is as simple as you get. Not using any of the 4th gen LS1 PCM, switches, sensors, etc.

BC

gagliano7

I am my 1992 truck a/c system and i connected the a/c request to the 1999 5.3 pcm but it doesn't change the idle when a/c is on. I just need to know what to connect so pcm thinks the a/c is on so it adjusts idle. So you grounded pin 55? My fans are controlled by flexalite kit so i don't need pcm to control fans.

Thanks Joe

1976CamaroGuy

iTrader: (8)

Just to verify with someone, will this switch when wired properly to the PCM activate the fans (via the relays) when needed through the Fan 1 and Fan 2 outputs?

I'm going to leave the Vintage air system hooked up as it's supposed to be, but use the computer to control the fans and engine RPM when the pressure switch calls for it.

I know currently the computer controls the fans off/on with the engine temp, through the temp sensor on the block

This is a DBC set-up.

Just wanted to check before diving into the wiring

Thanks

ls1nova71

iTrader: (4)

Depends on what OS you're running. If you are using a 99-02 F body, then yes, it will control the fans. But what do you mean by "leave the Vintage air system hooked up as it's supposed to be"? Vintage air doesn't use the PCM to control it, it's all stand alone. I assume you mean leave the A/C clutch wiring the way VA says to do it? If you're using the factory pressure switch, then I wouldn't do it that way, I would let it also control the clutch so that you get the benefit of high speed/RPM A/C cut off.

1976CamaroGuy

iTrader: (8)

It's a 2004 Truck PCM with both Fan outputs enabled. I've got another post describing what i was wanting to do.

Basically leave the VA set-up hooked up as they intended but use factory AC compressor sensor on the unused drier port. Running the three wires from the switch to

Pin Wire Color Function
14 RED/BLK A/C Refrigerant Pressure signal (A/C)
80 BLK Low Reference (A/C)
45 GRY 5 Volt Reference (A/C)

My thinking is, with the PCM settings for this set as they are supposed to be. This switch will send the PCM the call for raising idle or turning on the fans (through the fan control and relays already installed) when needed.

EDIT: I figured out 2003 + PCM's won't set up this way (like ls1nova71 stated). I'm gonna use a trinary switch to control the fans apart from the PCM instead

Hart_Rod

iTrader: (3)

I have a 2006 Tahoe PCM, Speartech harness, Vintage air, 3 wire truck pressure transducer, dual electric fans and, unless I'm missing something, the PCM is controlling the fans as well as the AC compressor based on the settings in that are programmed in the computer.

1976CamaroGuy

iTrader: (8)

Forgot about that post, i ditched the stock PCM and harness....running a Holley Terminator control system now.

All of that is being controlled by the new ECU