1072 c10 Fleetside tail lights

[1972chevc10]

I just purchased a 72 chevy c10 and got it running and everything. The plug at the back of the truck on the frame wasn't long enough because it has a different bed on it from the original. I have a wiring diagram and made extensions for it and hooked it up. The headlights and front turn signals work fine but at the back, when the left turn signal is on, the right one flashes and same for the right signal. Also, when the tail lights should be on with the headlights on, the driver side reverse light is on only. I have quadruple checked the wires i made go to the correct place. No brake lights work at all. I did a little work with the test light and hooked up my extensions and got the tail lights working along with the passenger side brake light and both turn signals are correct. All of a sudden, the brake light i had working stopped working, and so did the normal tail lights. The turn signals sill work though. The dash lights stopped working at the same time. My wiring behind the dash is all original and it has a new headlight switch and turn signal switch. The brake light switch has 12 volts on 1 of the 2 wires. With the headlights on, there is no power at the tail lights. The rear lights only work with the blinkers. Any help? I have tried and cleaned all the ground so that shouldn't be the problem. The fuses are all new too.

[snipescastle2]

it sounds like the wires got crossed somewhere in the main front to rear harness, usually when someone splices in a trailer harness, best bet is to download a wiring diagram for your model truck and trace the wires from each plug (one that plugs into the firewall and the other end ties into the rear tail light harness above the rear bumper-under the bed any way's) these plugs have four colors, light green, yellow, dark green and brown, I'll bet whoever did the splices just wasn't careful enough to get them in the right order.
The rear tail light harness is the one that seems to get hacked up more than any other part of the wiring. I was looking for a good tail light harness for my build at a local yard, and of course, couldn't find one. I looked at a clean 1980's model Chevy truck, and the plug that ties into the harness from front to back had the same plug on it (four pins kinda like a "T" ) any way's, the sockets were different, but essentially the same harness, I just cut off the newer sockets and spliced in the factory early ones. hope this helps....
Ben

[1972chevc10]

Thanks for the advice, but I have traced all 4 words from the plug at the back of the bed and none of the wires are cut and spliced. I forget to mention that I had to change around how the wires plug into the rear connector to get everything working when it did work. Sounds to me like in where it goes into the cab could be messed up. All the wire on the frame has no tape or anything and none of the wires are bad. They are all the right color too.

[snipescastle2]

the plug where it passes through the firewall, looks like the plug at the end of the long harness going to the rear light harness, this comes directly off the fuse block, unless they cut those wires, not sure what happened. good luck!
Ben

[1972chevc10]

I feel really dumb, it ended up being corrosion in the fuse socket. LOL

[snipescastle2]

Rust .....Happens.....