Trailer Lights

[Mike Quillici]

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?