Re: Trailer brake and turn lights work but not running lights
clean the ground, also check for shorts in the brown wire, that is the wire for the running lights. Also check your brown wire at the truck side to make sure there aren't any shorts.
Re: Trailer brake and turn lights work but not running lights
What is the tow vehicle??? Ford trucks (F150's and Expeditions) have a separate fuse in under hood fuse box which just powers the trailer marker/running lights.
Re: Trailer brake and turn lights work but not running lights
I had the same problem. I found out it was a blown fuse. Checked the fuses
under the hood and found a bad one. Replaced that and brought back my turn signals. Still couldn't get my running lights working. After checking further I found out there is another fuse box under the drivers side rear seat.
Checked there to find another fuse out. That fuse was for the running lights.
I have a 2004 GMC SUV. Check at your rear plug to see if your problem isn't comming from the vehicle.