1972 C10 no rear running, brake, reverse, or turn signal

[Cesar Diaz]

My 72 Cheyenne C10 402, 4 on the floor has been riddled with wiring issues due to tons of Mickey Mouse repairs. Including a wire that was installed from HEInto starter solenoid which made entire ignition Unfused circuit continuously live (Arrrrggg)

After cleaning up all wires and making sure everything is correct we have managed to get headlights and front running and turn signal lights to work, but rear running, tail, turn signal and back up lights do not work.

I've checked all the fuses checked for voltage at lamp housings (zero voltage) and am stumped. I traced the wiring that comes from the switch to back lights and tested with a probe no power going to rears at all. Since the power I believe comes from the switch I am guessing the switch may be bad but why no brake or turn signal lights. On a separate issue back up lights not working working either but want to fix running, brake,turn signal issue before I deal with backups in case lack of power is root of the problem.

Any thoughts? I'm not a wiz but I can trace a circuit.

Ps there was trailer wiring harness that was installed, I disconnected the wires and removed the trailer brake switch it was falling apart. It had 1 wire going to trailer wiring harness the other to power distribution block near the battery. What I don't know is if the lights were working before I did this.

We bought the truck not running in NM and trailered it back so lots of mysteries we are slowly solving.

[snipescastle2]

Those 4 wire rear light harnesses that connect the rear lights/brakes/back up/ license plate lights get pretty brittle after many years,they cack and possibly short over time.the plug starts at the firewall and goes down the drivers side frame rail back to the rear of the bed.good news is most walmarts have the four wire trailer light ribbon that's perfect for replacing this. surely your plugs are okay. I'd check your connections at the firewall for your rear lights first with a test light or multimeter and Go from there.a lot of times thes trucks have their rear light harness hacked up for trailer lights. But grounds can be a headache too.keep searching you'll get it figured out.
Ben Smith

[Cesar Diaz]

Gonna do that the wire appears to have been cut and poorly splice somewhere below the back of cab but there's no power originating from the firewall so problem I believe is associated with the switch. That is the only place it is hacked.
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