Well, I am helping a friend restore his Malibu and it came time to start the A/C wiring so we could button up the dash wiring. The problem is that every wiring diagram in my shop manual doesn't match the harness in the car and I am told it was a factory A/C car. Also, the wires that go to the engine compartment (Yellow, Orange, Brown, and Lt. Blue) have been cut. I can safely assume those are for the blower resistor. What I don't uderstand is the harness has no provisions to turn the the compressor on. all the wires terminate at the selector switch and the remaining wires are cut (for the blower motor assy). My question is, can somebody point me in the right direction so I can figure this out.

Hopefully I have provided enough information regarding my problem.

Something to consider--70--72 Chevelles the A/C harness is a seperate harness. It is not combined with the underhood harness. 70-72 The A/C harness comes out of the inside to the underhood by the dist. Bottom line in 70-72 Chevelles the A/C harness is another harness under the hood. I am not stating fact for your year. But I do know you cannot mix different year A/C harness. A 71 A/C harness will not work in a 70. I would check with a 68 owner to get more and better info.
I hope this may help a little. Bob ACES--AACA

What you need is an assembly manual. Page C60-E8 shows the wiring diagram that you're looking for. Assembly manuals are available on Ebay and at all of the restoration suppliers. This book is invaluable for working on Chevelles.
BillL

I will check for an assembly manual. As far as asking the owner, he is the one that cut the harness many years ago. I was thinking a little bit more and I am confused by a couple things. There is a brown and green wire that go to some sort of switch on top of the heater core box. Does anybody know what this is? I am assuming this is the compressor activation switch but I am not sure since there is absolutely nothing that looks like it would go to the compressor.

Dark green & tan (may look brown now) wires hook into the thermal switch that's mounted on the evaporator box. This switch prevents A/C operation when the outside temperature is below freezing.
BillL

These two wires don't go on the evap box. They go to a switch on the top of the heater core box, right next to the defrost vent.

Those go to the Diverter Door Switch, which trips based on the position of the door, whether its upper, lower, or bilevel. Light green should go to the fan switch BUT, tan runs through the firewall, and to the thermal switch as Bill said.


Yellow - pin 2 of blower resistor
Orange - Coil of AC relay
Lt. Blue - pin 3 of blower resistor
Brown - thermal switch (should be tan, I only mention because brown is another wire entire under the dash that goes to the fuse block)

To bypass the thermal switch, you could run the tan wire directly to the AC Clutch coil and the other wire for the coil should be grounded.

To wire it correctly, tan to thermal switch, then the other thermal switch pin should be dark green to the clutch coil.