73-87 LS Swap How to keep heat & defrost at least?
 

This may be a dumb question or I may be overthinking it.

I am LS swapping my 87 GMC V1500. Skipping dealing with ac for now, however, since I will be driving this winter, I need heat. More importantly I need defrost.

Doesn't the original run off vacuum or something for switching the blend doors or whatever?

I am assuming I can wire in the controller to the 01 wiring (I am using the entire 01 donor harness) in place of the 01 switch. So I will have power to the blower but what else is needed?

Re: 73-87 LS Swap How to keep heat & defrost at least?
 

It would be easier to keep the 87 under dash harness. You can get vacuum off the small port on the passenger side of the intake for the blend doors and such. That is if youre using a truck intake, car intakes the vacuum is in the rear of the intake.

Re: 73-87 LS Swap How to keep heat & defrost at least?
 

All of the 87 harness is gone (as in it has already been removed, I still have it off to the side. I can get the plug end from the 87 harness). I already have integrated the entire 01 harness in. It powers my power windows, locks, mirrors, all lights and so on.

My only real options to power the 87 heat/ac controller is either wire it into the 01 fuse box manually or just cut/splice into the plug end for the 01 controller.

So is that what everyone does then, just tap into some vacuum port on the PS side of the intake? I got to find that port then I suppose.

I originally wanted to try and put all the 01 ac/heat stuff in, but it is too big and I didn't want to have to modify anything too heavily so I am keeping the 87 stuff. Eventually I will get the 4.3 AC bracket and hook up my ac but that will be probably next spring. All $ is going into getting her road ready for the winter.