Trailer Lights Not Fully Working on a Trailer Towed by a 2007 Ford F-150 with Factory Tow Package

Question:

Well I have F150 2007 Have ford Traiker ligts Harness and Before I changed it I had turn signals and brakes Never had running Lights. Know I have a new harness and I only have turn signals on one side and brake lights on one side. I will try cleaning ground one more times and hooking truck to trailer to see if I can get it tow work does this sound like a grounding problem or connector, ?

asked by: Joe

Expert Reply:

It does sound like a ground problem. Most wiring issues are due to a bad ground connection. But first, I do recommend checking the trailer and vehicle side connectors for dirt or corrosion in and behind the plugs. That can cause the problem as well and it is the easiest thing to check.

After that, if you still have issues, start checking all of the grounds starting with the truck side trailer connector and working back to the tail lights on the trailer. The grounds should all be connected to clean, bare metal surfaces that are free of dirt and corrosion.

Trailer tail lights ground through the mounting studs unless there is a ground wire present. You can also check for nicks or breaks in the wiring.

If you have recently added a plastic license plate holder, that can cause some problems if the tail lights do ground through the mounting studs. I have included some links to some videos that you may find helpful.

expert reply by: Michael H