WhiteBlaze

iTrader: (1)

Hey guys,

Been searching about this the past few days. My car is originally a V6 car, and it now has an LT1 in it. I'm trying to get my A/C wired up now. The company that "converted" my harness, has an A/C request wire, but a relay cannot be found. Also, my accumulator only has a two wire switch. So to get this to work properly, from what I've read, I need to get a pressure sensor from a 90's front wheel drive car - this has the correct sensor to work with the PCM and the correct threads for the accumulator. Then I will need to acquire the proper pigtail, since I only have the two wire one on my car. A relay will also be needed.... correct?

I also came across this https://www.thirdgen.org/forums/ltx-...ng-i-need.html (#13) post. Its for an LS1, will it also work for an LT1? I understand the pinouts on the LT1 PCM are different, but I have no problem finding that out myself.

Pocket

iTrader: (24)

A relay would be nice. It takes the voltage load off the PCM and transfers it to the IGN system. Truck LSx PCMs dont use one, but relays are cheap why not

Grab a AC pressure switch from any late 90's GM car or TPS connector like on your LT1. Remember, the switch connector goes to the PCM. The relay feeds the compressor clutch with a redundant wire to the PCM

Yes, the info in that post also pertains to LT1s, here are the necessary diagrams for your LT1

http://www.lt1swap.com/all_lt1.htm

Z28ricer

iTrader: (2)

Use the stock thirdgen cycling switch, and stock style wiring, no need to reinvent the wheel.

Firebat

iTrader: (7)

There are 2 basic ways that it can be wired. Low pressure switch controlled or computer controlled.

The easiest way would be to use just the thirdgen low pressure cycling switch for the a/c that is mounted on the side of the accumulator. One wire goes to your a/c switch panel in the interior, the other goes to the a/c compressor. Also the a/c compressor green wire would not have to be connnected to the LT1 pcm wiring, just the switch. A relay and the high pressure switch are optional upgrades to get the a/c to work but not required. Look over the diagrams below:
http://92b4crs.tripod.com/86wiring/dia-pics/63-4.jpg
http://92b4crs.tripod.com/86wiring/dia-pics/63-7.jpg
Note that your stock wiring may differ because some thirdgen setups used a ecm-controlled relay or a power-steering switch in place or addition to the high pressure switch.

The more difficult way would be to use the PCM along with a 3-wire a/c sensor (not a switch). The only real benefit I see is that the PCM would adjust RPM at idle when the a/c is on. I've talked about how to get this to work in these threads:
https://www.thirdgen.org/forums/ltx-...h-gen-ltx.html
https://www.thirdgen.org/forums/ltx-...r-control.html

I recommend the easy way and just using the cycling switch

WhiteBlaze

iTrader: (1)

Any ideas on how to wire it up so my cooling fan kicks on? Using the "easy" way.

TexasLT1

Yes, you would just wire the 2nd fan relay to the same wire that turns on the a/c compressor clutch. Unless you only have 1 cooling fan, then no.

WhiteBlaze

iTrader: (1)

Ok..... well, I only have one fan, so looks like I'll be doing it the computer controlled way.... thanks!

Pocket

iTrader: (24)

Fan relay is expecting to be grounded to engage, AC request sends 12v when your HVAC head is switched on. Tee into that wire and use a relay to switch the 12v to grd

WhiteBlaze

iTrader: (1)

The pcm will be ok if the ac has the fan running, and then it requests the fan run due to temp? I just don't want to fry anything.