72 Air Conditioning
Thread Starter
Intermediate
Joined: Mar 2011
Posts: 27
Likes: 0
72 Air Conditioning
OK, ready for my next project, getting the AC on my 72 (base 350) working. I have lots of wires not connected to anything, and many seem to come from the AC harness. Here's my question:which color wires run to the three prongs on the thermal limiter for a 72 vette? where do they come from? there is also what looks like a 12 gauge orange wire not connected to anything, it disappears into a harness that does not seem to service the AC. i have a wiring diagram for a 72, but the only one with AC i can find is a 74, and its different. it doesn't show the black wire running to the nipple connector on the back of the compressor. Thanks.
Pro
Joined: May 2006
Posts: 567
Likes: 5
From: bradenton fl
i can check for u tonight. Will be home from trip
I do know its 2 green wires from harness and 1 black wire that goes to the back of compressor with a pin connector
I do know its 2 green wires from harness and 1 black wire that goes to the back of compressor with a pin connector
Last edited by 72ragtop; Mar 20, 2014 at 01:50 PM.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
The orange wire runs the high speed fan it connects to the fan relay that is on the evaporator housing. The other end runs to the driver side to the horn relay when it connects to the horn relay the wire is red. Follow the red line to a inline fuse a short distance away the the horn relay. Notice that one side of the inline fuse is red and the other side is orange. 
Cruising
Joined: Mar 2014
Posts: 14
Likes: 1
Based on the wiring diagram I have for my '72 the three pronged thermal fuse (thermal limiter?) connects to the Green-->Green-->Black wire harness. The first green wire leads to the A/C Compressor, the second green wire leads to the Evap Thermal Switch and the black wire leads to the Super Heat Switch which is the nipple connector on the back of the A/C compressor.
I think the orange wire you are talking about is part of the ignition harness and is for the blower motor on non-A/C cars. I say this because my car came from the factory with A/C and I have the same orange wire hangin' out in the engine bay and I couldn't, for the life of me, figure out where it goes. Apparantly the A/C harness has a separate purple connector for the blower.
Hope this helps! I would definitely recommend the wiring diagrams from Doc's Rebuild website. They're around $20 but are a lifesaver as he has photos of each connector, wire color, harness, wire gauge, etc. Has helped me solve quite a few electrical gremlins in my '72.
I think the orange wire you are talking about is part of the ignition harness and is for the blower motor on non-A/C cars. I say this because my car came from the factory with A/C and I have the same orange wire hangin' out in the engine bay and I couldn't, for the life of me, figure out where it goes. Apparantly the A/C harness has a separate purple connector for the blower.
Hope this helps! I would definitely recommend the wiring diagrams from Doc's Rebuild website. They're around $20 but are a lifesaver as he has photos of each connector, wire color, harness, wire gauge, etc. Has helped me solve quite a few electrical gremlins in my '72.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
The orange wire is for your "High Speed" fan. When the fan switch is all the way to the right.
Your fan will run without the orange wire just not on high.
Your fan will run without the orange wire just not on high.
Last edited by Roco71; Mar 21, 2014 at 07:24 AM.
Pro
Joined: May 2006
Posts: 567
Likes: 5
From: bradenton fl
Roco, the orange wire comes off the ignition harness to the blower on a non a/c car. The purple wire to the blower is on the a/c harness. My orange wire it cut and my blower works on all three speeds with purple wire attached.
May be different on a 71?
May be different on a 71?
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Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
71 has a different a/c harness I believe its because of the anti dieseling relays that kick the a/c compressor on for 3 seconds when you shut the engine off. I am sure that the orange wire is the same on 72 as 71 for high speed fan. (I have been wrong before) 
I think you may have 4 speeds on your fan.
I think you may have 4 speeds on your fan.
Last edited by Roco71; Mar 21, 2014 at 12:49 PM.