I have been having problems with my trailer lights. After reading several old and recent threads I decided to just get a new wiring harness kit and rerun the wires (the lights are pretty new). Just as others said, replacing the wires was easy. My brake lights work and my turn signals work perfectly...but the trailer lights do not light when I turn my SUV headlights on. Any ideas why the trailer lights don't turn on when I turn my headlights on? I have a five pin setup on the boat. My Nissan Xterra has a seven prong connector and I have an adapter to connect boat to car. Thanks for any help you can provide.

I thought it might be a weak ground, but I have regrounded the lights to the trailer and no change.

If I recall correctly,Brown is trailer running lights,check to make sure your have power on the 7-5 connector. Did you check fuse on truck side?

That was my problem on a new Expedition.

Mine has separate fuses on the truck for the trailer plug wires and truck taillights also. Bare turn signal wire on trailer blew fuse and I fixed wire. Truck turn signals worked but trailer didn't. Finally found out the trailer and truck lights each have their own fuses. Good idea cause you won't loose all lights if one shorts out.

Thanks guys. Will definitely check.

Brown is running lights
see if it is getting fire
tract the fire from the plug to the light

Sounds like a test tight would be a good investment.

Bulbs good?

Anytime you're working on trailer lights, make sure your trailer is on the car's hitch. More often than not, that's the ground path for the wiring. My ground wire was just capped and I couldn't figure it out for awhile til everything started working when I had the boat hooked up.