OK, so I am swapping an LS1 with T56 into an 89 trans am TBI. The dude that built my wiring harness unfortunately did not include some of the stuff I need, so I am going to have to re-pin some of the outputs. I relatively sure it will be ok, but i'm just running it by those of you that have done this already...

I've decided to use the LS1 compressor and there are no wires for a/c request/pressure switch on my harness. Here is a diagram of my 89...


So, since my TBI is vin E, it looks like there is one wire that communicates with the ECM. I was planning to just hook this up to Pin 17 on the red 2001 LS1 PCM connector (A/c request signal), and use my old thirdgen stuff (just swap connectors for the compressor) Does this work, or do I need to fiddle with/add the LS1 pressure switches, an a/c clutch relay, etc.

Ok, my other question is for the cooling fan. I'm just hooking up the lead from my old coolant fan switch to Pin 42 of C1 on my 2001 PCM. (low speed cooling fan relay control) I'm leaving the stock relay, and using the TBI single fan. I believe most people do it like this. Any issues?

Thanks for our help, the info available on this board was huge in getting me this far.

 

You would need to hook up the A/C request signal from the HVAC switch to the PCM, wire in the A/C compressor relay, as well as the pressure switch. I think you just need the high pressure switch for the LS1 setup.

As for the fan, what happens when the PCM switches to the high speed cooling relay? Your low speed will quit. I would hook up both high and low to the fan relay lead, so when one turns off, the other keeps it going.

 

on my harness i currentperformance.net do mine. but he didnt give me a pressure switch connector for my 92 style a/c compressor. do you think i will have a problem?

all i have to do to hook mine up is splice in the a/c request. and that should do it.

but no pressure switch. would it be ok?

 

Well, it is my understanding that if your A/C compressor is running and it has no sensor to turn it off when the pressure becomes high... boom.

 

oh snap. this is bad.

 

Yeah, i ran wires from both the low and the high speed outputs, and i am running them both to my fan relay. They both just ground the circuit when activated, so hopefully nothing kooky happens. As for the AC, the diagram for a 2001 trans am is below. Doesn't look too bad, i just need to add a relay. My only concern is if i can reuse the TBI hi pressure switch or if i need to get myself an ls1 switch. ( i don't see a 5 volt reference for the TBI, so the signal miht be different) I don't think the LS! sensor is too expensive, i am most likely just going to wire it all up with LS1 stuff just to be safe.

On another note, if any of you have C100 and C207 out of an 89 t/a tbi, it would be much appreciated. It was one of the only diagrams i wasn't able to find on mitchell. I also have GM techline and omst of the 89 firebird wiring if you want to trade diagrams, thanks.