Factory AC wiring harness ID

[jumpsoffrock]

I have access and bought two old used factory AC harnesses presumed to be for 67-72. I have found a couple "extension" wires that I really want to know what/why there are there.
I was able to look at two more factory AC trucks in the guys yard, both trucks also had the red wire going somewhere but I don't know where.

There is a plug that the factory manual says goes to the "cig" male connector in the fuse panel. This main orange wire goes to the heater relay.
That wire "Y"'s twice. First into a red 12 GA wire that ends in some kind of nipple connector. The other extends into yet another connector going nowhere circled and pointed to in green.


Can someone tell me what the red wire and orange extension plug are for?

[jumpsoffrock]

hdff posted a pic in a thread that explains my question. The nipple connector probably goes to the cigarette lighter since the AC wiring harness is supposed to be plugged into the "Cig" plug in on the fuse panel.

I always thought that 25 amps being allocated for the AC was rather high for simply engaging the compressor clutch but if the circuit also services the blower motor and the cig lighter, I can see why the "AC circuit" allocates 25 amps now.

http://67-72chevytrucks.com/vboard/s...d.php?t=695379

[dmjlambert]

Yes, the A/C fuse is going to run the fan on low and medium speeds. The high speed is handled by the unfused CIG position at the fuse panel. There are 67-70 and a 71-72 wiring harnesses because in the later years the anti-dieseling relay was added. Mine is a 69 and does not have the anti-dieseling relay.

69:


71:


The various years service manuals have the diagrams in the A/C section. The 69 diagram is from my paper manual.

I don't know that anti-dieseling is anything to worry about with modern gas. I have not seen/heard an engine dieseling in years. If you have a 71-72 truck you could probably just leave out anti-dieseling stuff.