RE: Brake lights don't work on trailer...
If the newer trucks have the same setup as the older Dodges, it doesn't have a ground at the back of the truck. My guess is whoever set up the lights for you didn't do the brake light wire correctly. If I'm not mistaken, there are four wires, one of the brakes, one for each turn signal, and one for when the head lights on on. I can't remember the exact color, but the brake light wire should be on one of the ends of the light plug in if it's a four pin plug. But as others have said, check all the wires with a test light.
1992 Ford Ranger XLT. 4.0L V6, A4LD auto trans, 4X4, extended cab. Lund Sun Visor, Huskey Tool Box, Sony MP3 play back head unit, rest is stock!
1995 Dodge Ram 1500. 5.2L 318 V8, 5 speed manual, 4X4, single cab short box. No mods as of yet, and