When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Now that I’ve had the corvette driving again I’m trying to go through and fix the bubbafication the PO has done. So in their eternal knowledge of how to royally screw all future owners of the car they went through and cut out a good chunk of the harness, the factory AC being one of them. They cut all components of the AC out aside from the box and the console controls and some wiring coming from the relay on the passenger side firewall next to where the box would be. Which has since been removed and a block off place has replaced. So my question is, what wire needs to goto the blower motor and would hooking the blower motor up at least give me heat for the defrost and at least attempt to warm the car on the inside? Or even more would putting the box back on then running new lines and getting a new condenser give me both heat and ac again, or is that just a lost cause at this point and should go for vintage air for the future and worry about heat for now?
Edit: I always forget to include it’s an 1981
Last edited by Ethan_Hensley; Oct 10, 2025 at 03:47 PM.
Here are some question for OP...
1. Do you still have the firewall heater box and blower motor in the car?
2. Did previous owner remove or cut all the wiring from cabin controls to engine compartment, if cut what's left? A photo would help...
Personally, if it were me and I just needed heat I would replace the fan speed selector switch with a new Non AC switch GM #362536 ($25.00-$35.00 US) and a heater blower resistor for a non AC car... Napa part number ECH BR430 ($18.00 US)...
Below is a 1979 wiring diagrams for both NON AC & AC cars...
Now, OP will still have to work on vacuum actuator hoses from control vacuum switch...
I don't see a easy way especially not knowing what's there and what's not...
Something like this, NON AC drawing Left, AC Drawing Right and the changes I would make...
If they didn't pull all the engine compartment wires for the AC, there should be still something left there to work with...
Here are some question for OP...
1. Do you still have the firewall heater box and blower motor in the car?
2. Did previous owner remove or cut all the wiring from cabin controls to engine compartment, if cut what's left? A photo would help...
Personally, if it were me and I just needed heat I would replace the fan speed selector switch with a new Non AC switch GM #362536 ($25.00-$35.00 US) and a heater blower resistor for a non AC car... Napa part number ECH BR430 ($18.00 US)...
Below is a 1979 wiring diagrams for both NON AC & AC cars...
Now, OP will still have to work on vacuum actuator hoses from control vacuum switch...
I don't see a easy way especially not knowing what's there and what's not...
Something like this, NON AC drawing Left, AC Drawing Right and the changes I would make...
If they didn't pull all the engine compartment wires for the AC, there should be still something left there to work with...
1. Yes I bought brand new heater core if that’s what you mean by heater box and blower motor when I put the block off plate on.
2. It seems all the cabin controls wiring is intact under the console and out to the relay on firewall. I will send pictures in the morning when it’s lighter outside of what’s left coming from that harness. I’ll attach an older picture I have from when the box was still in the car to show the hard lines that were cut out of it.
From what I could tell when I took out the evap box a couple years ago the wires going to it were still plugged in and attached but I don’t believe the blower motor was plugged in ever.
1. Yes I bought brand new heater core if that’s what you mean by heater box and blower motor when I put the block off plate on.
2. It seems all the cabin controls wiring is intact under the console and out to the relay on firewall. I will send pictures in the morning when it’s lighter outside of what’s left coming from that harness. I’ll attach an older picture I have from when the box was still in the car to show the hard lines that were cut out of it.
From what I could tell when I took out the evap box a couple years ago the wires going to it were still plugged in and attached but I don’t believe the blower motor was plugged in ever.
As long as the high speed blower relay & blower resistor are still in place and wired with no faults the blower motor and fan speed switch should work.
You have a mess there...
If you don't have a Multimeter get one, a cheep hobo freight one will do for now.
I have studied your photos and will do my best in describing where I "THINK" they may land, or where the once landed...
Again, check with Multimeter before energizing "ANY" circuits...
I have added colored arrows to a 1980 AC drawing.
The arrows have a number inside them on what or where I "THINK" they once landed...
Hope this makes sense...
Your 3rd photo I have no idea, other than it's the blower high speed relay...
Drawing:
You have a mess there...
If you don't have a Multimeter get one, a cheep hobo freight one will do for now.
I have studied your photos and will do my best in describing where I "THINK" they may land, or where the once landed...
Again, check with Multimeter before energizing "ANY" circuits...
I have added colored arrows to a 1980 AC drawing.
The arrows have a number inside them on what or where I "THINK" they once landed...
Hope this makes sense...
Your 3rd photo I have no idea, other than it's the blower high speed relay...
Drawing:
Awesome! thanks for the mark up! Unfortunately my work week has started so I will continue the hunt Thursday and report back.
Additionally; if the blower resistor (Yellow 1) is still connected to the harness it needs to have an encloser or at least insulated from the elements...
Purple 4 I believe comes from the blower motor resistor (Yellow 1) and supplies voltage to the blower motor. If you test voltages there you will NOT get full 12vdc unless your fan speed selector switch is in the HI position...
Additionally; if the blower resistor (Yellow 1) is still connected to the harness it needs to have an encloser or at least insulated from the elements...
Purple 4 I believe comes from the blower motor resistor (Yellow 1) and supplies voltage to the blower motor. If you test voltages there you will NOT get full 12vdc unless your fan speed selector switch is in the HI position...
Good to know, yeah I think I’ll have to order a new resistor or pull it off of the old ac box and find a way to mount it and protect it.
Theonlyreason for the resistor is if you hear a winethrough your radios speakers...
Most modern systems if wired and powered from the battery you wont hear the wine...
I thought you were talking about the radio resistor at the blower motor itself.
Yes, you will need a resistor to make the blower motor run. That is the circuit path to the blower motor...
Heat/AC question (electrical mess)
