Thanks to the wealth of information here in the forums I've completed an LS1 swap into my '92 GTA, however it looks like I've missed something. The HVAC blower doesn't work.

Since I suck at wiring and didn't want to screw anything up I had HawksThirdGen do my wiring harness while I did all the other changes and modifications to the car prior to putting the engine in. Once I got the engine in and harness attached it looks like I missed a step. Attached pic is all I have to go on for how to hook up the blower.

Is this telling me to run a wire from there directly to the battery? Is it the red wire that goes into the relay next to the blower motor? The harness Hawks sent already has an extra red wire running down to the starter where the positive battery terminal connects. Do I need to add another one for this? I don't really get what he's trying to show me here in these instructions.

 

90-92 cars had 3-4 wires in the hvac connector

12ga red is battery 12v for the blower
12ga blk is grd for the blower
18ga lt blu is Ac request
18ga dk grn/wht (sometimes missing) is fan relay override. It is not used in the swap

82-89 cars had the 12v wire divorced from the hvac connector for optional inline hood light mini-harness. Early cars used a different connector. 12v, grd and Ac request are all that's required for a swap, so use a test light/meter to find the wire with 12v when Ac is selected

Non-Ac swaps only need 12v and grd for the heater/defrost to operate

3rd gen hvac mini harnesses have two vacuum lines. The longer one went to the diverted valve. Ghetto cruiser has a good thread on retaining this if you want. Cap it if deleting. The shorter vacuum line feeds the hvac head unit and is split to the various flapper doors. LSx engines have a small port on the rear of the intake for this. Lt1s have multiple ports available. A check valve is recommended. Without this connected, only defrost will be available

That's everything related to hvac connections anyone will need to know for a swap

 

I got my harness from Hawks too. Here's a couple pix of the connections I made for the hvac. I agree the instructions were confusing. At least yours had color photo's!

First picture: My '88 had a red wire that needed battery power. I made a wire by soldering factory connectors at both ends so I can disconnect easily if needed. Not pretty, but totally functional.

Second picture: Shows where I spliced the green wire on the Hawks harness into the third gen hvac harness for a/c request.

Third picture: 3-wire connector on Hawks harness hooked to 4th gen pressure switch I got from my donor car. The switch just installs in place of the 3rd gen 2-wire switch.

I also had to add a ground to the blower motor.

 

Thank you! This worked. Now to figure out where to put the vacuum that comes out of the firewall so I'm not stuck on defrost all the time. Any suggestions?

 

There's vacuum available on the back side of the intake manifold near the MAP Sensor. I tried to snap a picture of my vacuum connection. It's pretty tight back there & difficult to show any context. Hope it helps.

 

That does help. I think my engine harness is in the way but I should be able to get my fingers back there. I probably should have put that on while I was installing the engine. The pics are great, thank you.

 

Hey man , I was told you can make a plug and play harness for a ls1 in a 3rd gen ? Wanted to know if you will and how much you will charge

 

I called Hawks Motorsports and had them do it. It cost me about $1000 but that was in 2014 and I dont know if that's changed. Give them a call at 1-864-855-2694. They are awesome to work with.

 

I'm assuming you have to now fuse this wire since it's no longer being fed power from the fuse block under dash?

Tossing in the hvac right now and have found I have zero power to the box. I did find the red wire that I tapped up and shoved into the heater hose.