Taillight Problem...Please HELP!

[Longhorn Al]

Let's see if I can explain this at all. haha

I don't know what it is called. When I bought my truck it had a trailor brake system installed (no idea what they are called). It has the little box deal mounted under the dash on the left. Push on the brakes, lever moves to the right and little red light comes on.

Ok, recently, when I turned on my head lights, the headlights would come on. But the taillights, rear side markers and dash lights would not. Flashers and blinkers worked. Not sure about the brakes.

My dad and I messed around with it and replaced a fuse. Everything started working again. Two days later (now), the problem is back, but with a strange twist:

I have my headlights on (taillights and dash don't work obviously). Now when I brake, and push that little lever on the box over manually, all my lights come on. I can only do this while stepping on my brake. When I step on the gas, the lights go out. And they only come on when I manually pull that lever over (and it's pretty tough to do).

Also, my back up lights have never worked properly. One is out and the other blinks. But that is another problem that is not as important.

Please HELP ME!!! Thanks.

[barn9]

The first thing I would do is remove that trailer brake and put it in the proper container, the trash can. Sounds like the problem most likely is where it was spliced into the regular wiring, anyway that is where I would start. I know when I bought my truck, the rear wiring harness had been spliced so many times for trailer lights that it looked like a nightmare in electric-land. I got a new rear harness with the trailer light adapter that plugs in between the rear harness and main supply plug, and everything works perfectly, including backup lights and side markers. It wasn't cheap, but it was the proper fix with no worries. After getting that old harness out, there was no doubt it needed to be replaced. One thing to remember, that old wiring is now 30 years old, and a lot of the old protective coating is cracked and brittle, which leads to further deterioration. After all was said and done, I was glad I spent the money and fixed it right.

[TERRYP]

The hydraulic trailer brake device has a switch that lights up the red light, and sends on/off voltage (along with variable voltage thru another wire) out usually the red wire. You should be using your regular brake switch, not this voltage.

[COBALT]

I've been a victim of this too, only my previous owner didn't even bother to have a dedicated harness put in, or the manual switch. They just hacked into the hot side to provide a constant 12v to the rear. Of course it shorted out and blew the fuse all the time, so one night I just tore out everything that was done, and patched everything back together according to the wiring diagrams for the '69. Everything works just fine now.

Funny how that works.

[bobs409]

I agree in that your best to remove all that garbage and start fresh with a wiring diagram in hand! I just fixed all the wiring on my truck and used a copy of a diagram found on the net. http://www.geocities.com/chevroletc1070/wiringdias.html

By the way, I found that my truck already has a wiring plug for a trailer. It's original and has 4 wires; 1 for brake, 1 parking light, 1 reverse and the 4th I believe is a ground.

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Barn9-The first thing I would do is remove that trailer brake and put it in the proper container, the trash can.

That cracked me up! LOL