Rear harness/rear lights not working

[cgster]

Been piecing my truck back together and have all of the front lights working but not the rear lights.
The rear brake lights, reverse lights and rear side marker lights are not working. Turning on headlights does nothing for the rear lights. The left and right blinker on the rear lights work. I have hooked up the ground wires for the marker lights but nothing. Any ideas what im missing? Also, this is for a 72 C10 Stepside. Thanks.

[03BlkZ]

Originally Posted by cgster

Been piecing my truck back together and have all of the front lights working but not the rear lights.
The rear brake lights, reverse lights and rear side marker lights are not working. Turning on headlights does nothing for the rear lights. The left and right blinker on the rear lights work. I have hooked up the ground wires for the marker lights but nothing. Any ideas what im missing? Also, this is for a 72 C10 Stepside. Thanks.

Are you using a new or original harness? I would also run a couple of ground straps from the bed to the frame. Grounds are very important on these trucks. Double check harness disconnect at the rear of the truck and make sure it's fully connected. Also are you using stock type bulbs or LED?

[rockyrivermark]

First thing to do is check to see if power at the various lights with a cheap lighted tester attached to good known ground. Even run a long wire to negative on battery if necessary
If no power trace back until you find the issue. If you have power at the socket then fix the grounding issues.

[pjmoreland]

Sounds like you might have multiple separate issues. One thing that stands out to me is that your rear turn signals work, but your brake lights do not. These use the same lights. That indicates the wiring from your turn signal switch back to your brake/turn signal lights is good, and at least your brake light housings are grounded. I'd be looking at the fuse, brake light switch, wiring that runs from the fuse panel to the brake light switch, and the wire from the brake light switch to the curved connector of the turn signal switch.

[Accelo]

You can check for voltage at the plug under the dash. It enters the cab right above the throttle. If you have voltage at the plug, you know the switch is good and the issue is a wiring issues at the rear.
There should be a ground at the back of the box on the bottom of the last support on the left side. You may find the ground eyelet is there and the strap is missing. Common on these old trucks. Even though the brake and turn light’s function, I would confirm the ground to eliminate future issues. Don't forget to check the bulbs. I have watched people do a ton of electrical trouble shooting only to find out the bulbs were bad. Prove everything and you will find the issue. And remember low voltage DC always requires cleaner connections than common AC circuits.
Rick

[bob arrington]

check your ground at the very rear section of the harness, this is pretty common in areas of the country where rust occurs