So I was going through the harness this weekend. I've got the Holley HP system and harness on order, and of course in 89, the engine harness is integrated with the rest of the car, so I'm doing some house cleaning. I came across this harness, which is in the pic. Looks like from what I can tell it's ONLY for the HVAC. It's got the fan and thermostat pigtail, a hot 12v pigtail, a relay, vacuum lines for the diverter, and as far as I can tell, it's just HVAC.

Can anyone confirm this?

I dont' run heat or AC, but I DO use the vent fan. I was gonna remove the harness and rig up a custom stripped down version so I only had the fan. Don't wanna lose something else that I'm not aware of.

 

Yes that is for the HVAC exclusively.

Black oval box is the high speed blower relay; gray plug is for the speed resistors; plug w purple & black is for the blower motor; etc. One of the vac lines is "supply" to the control head, other is for the heater control valve.

 

Sweet. Thanks for the quick reply. I figured it was HVAC only, but knowing GM, they'd wire in something else important, just for fun.

 

Since everything is easy to access right now you could install a non-AC wiring harness while your in there. They are nice and simple harnesses,.. no relays, no extra wires; just simple power and ground to the blower motor and a 3 prong resistor pack. ( would only give you 3 blower speeds. )

I should still have 1 around here somewhere if your interested.

 

That's an interesting idea.....let me think about that.