I got my new trailer today and had no running lights but everything else works great. I checked the 4 pin and the 7 pin and there is no power to the brown (running lights) wire. What should I do? I even went up the harness a few inches and spilt the wire loom and checked with a test light; nothing at the brown wire.

 

Check the fuses. There are more than one for the trailer wires.

 

On my trailer, the running lights and the tail lights shared the same power wire. If one is working and the other not, then you might need to look closer at the trailer wiring. I had to virtually re-wire my trailer as I could not trace where the break in the circuit was (too many places where the wiring went into inaccessible areas).

As I am sure you will find out, the biggest cause of these problems is a bad ground somewhere. Good luck with it.

Neil

 

It turned out to be the trailer, it had a short and was blowing the fuse on the truck. The #33 fuse (trailer park lamps). By the way, that was my first experience with the fuse panel and boy was that thing big, 77 fuse locations wow!