Non AC to AC Wiring

[79Betty]

On my 79 k10 the outside wiring (firewall forward) is non AC. The in cab wiring harness is from a 78 k20 without AC and it is mint. Not a single spliced wire! My dually i'm using for parts is an AC cab with all that, stuff. How would i wire them together to work as normal? Is it plug n play? I'd use the dually wiring but mice and the PO turned it into such a giant mess i can't make heads or tails of it. Thanks in advance guys.
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[SamsAutoParts73-87]

it should be plug and play, as long as the fuse boxes are the same all the connectors should the same.

you will need to unplug the heater harness from the cab harness (it is a single connection behind the gauge cluster. The A/C harness should plug in its place, and possibly the fuse box.

in the engine compartment, there is a wire that attaches to the junction block on the driver side firewall.

I need to look and see if I have any pictures of the 78 K10 I parted out, it had A/C and I thought I took pictures for the guy I sold the A/C setup to.

If I forgot something, please feel free to correct me.



-Sam

[chengny]

There are some differences. A couple that come to mind:

The low pressure cut-out switch has to be wired into the compressor clutch circuit.

The blower resistor is a 4 terminal type as opposed to the 3 terminal on a straight heat system.

The A/C system has a blower motor relay - plain heat doesn't.

Here are the wiring diagrams for A/C and non A/C:





Here is a suggestion - If your dually parts truck has an A/C system - just pull that and change the project truck over from the dash/fuse block all the way out to the engine compartment components. That procedure is real simple and would be truly plug and play.

[79Betty]

The wiring is so hacked it's sad. Every wire is black, and they used 3-4 secrtions of wire to just make it. Somebody was either ignorant on what they were doin or just plain didn't care. I can wire somewhat decent and i'd rather just add what i needed. Plus i have looms of all colors so it will look correct instead of 15 black wires taped together
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[79Betty]

Little update for everyone. I'm not touching the ac wiring on the firewall yet , will see what happens there. Put in my 78 k20 harness, high low beam in. Spliced in 77 washer switch, got it taped. When i pulled the 77 harness it DIDN'T have a plug at all. Only one brown one with a single wire. My 78 has the same but it's orange n brown tied together? I'm gonna go through the 77 and make it look brand new and wind up goin with it a later date. Fyi lol
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