98 ram 1500 318 4x4.

So I replaced my trailer harness on my truck for all my new lights on the trailer I just bought. So I wired up my trailers lights and put my new harness on the truck and I get normal running lights but when the running lights are on, hit the brakes, and the trailer lights go out. Would that be a wiring harness problem?

 

Sounds like the trailer harness on the truck or the trailer lights are wired up incorrectly. Also, check to ensure your ground wiring is good and tight.

 

Yeah. I just figured it out. It was the ground I had on the trailer tongue. The wire broke off when I retightened the bolt I grounded it to

 

Glad that's all it was. Thanks for sharing the solution.

 

Not a problem. I felt pretty stupid for not checking that first. I almost started taking apart the new harness I just put on the truck itself and redo it all over again. Fortunately, I found the original factory harness wires were still good, so all I did was cut off the old 5 pin connection, used 4 of the 5 wires that were necessary, and went from there. Everything works PERFECT now.