Trailer Lights
 

I have a boat trailer that I know is wired correctly, because I have towed it with several other vehicles, and have never had a problem. When I hook it up to my 72 C-10, however, something isn't right. Turn signals appear to work fine, tail lights appear to work, brake lights appear to work, but when the tail lights are on and I press on the brake lights, the trailer goes dark. When I let off the brakes, the tail lights come back on. When the tail lights are off, the brake lights work fine. The only other thing that I have noticed is that the brake lights and turn signals are dim. . .Ground is solid.

I'm not sure what's going on, but clearly something is crossed on the truck side. Any ideas?

Re: Trailer Lights
 

Do the other rigs you tow it with have turn light bulbs that are separate from the stop light bulbs? If the trailer is set up for those it "might" cause an issue.

2. How big of a basket of snakes do you have under the back of the truck for trailer wire hookup. It seems that on almost every old truck I buy I end up cutting all of the previous owner's trailer hookup out and rewiring it to make it work.

Re: Trailer Lights
 

1. No, I just have my boat trailer.

2. And I just cut out about 10 feet of useless wiring and wired up my own wiring harness. I did a little research, and apparently this is a very common problem associated with a bad ground, so my statement in my first post may be incorrect. I am going to re-ground both the truck and trailer tonight, so we'll see what happens.

Re: Trailer Lights
 

I'll put in that the symptoms are those of a greound problem.It sounds like the lights are grounding thru one of the other circuits when power is applied.If both circuits are powered,there's no place to ground.If you have a "flat 4" plug,they make a tester for it that only costs a few dollars.The 4 wires should be
Left turn
right turn
tail lights
ground
The brake lights work thru the turn signals.They function as brake lights until the flasher (for turn signal) interupts the circuit causing them to flash.This happens one at a time with turns and all at once with emergency flashers.

Hope this helps.

Re: Trailer Lights
 

It was a bad ground. All fixed and reattached. No more problems. Thanks everyone.