Running Light Circuit on Factory Trailer Connector Not Working on a 2010 Ford F-150

Question:

This weekend when I hooked up my trailer the running/tail lights wont work. Turn signals and brake lights are fine. It has a factory installed 4 wire connector. I have voltage at the connector on the turn signals and brake light, but not at the running lights. I have owned the truck since it was new and the first time Ive had a problem. Is there a fuse for this circuit? Lights on truck work fine. Thanks

asked by: Mike M

Expert Reply:

Your 2010 Ford F-150 does use fuses for the tow package wiring. It could also have relays related to the tow package wiring. Use the vehicle owners manual to find the locations to check them. It does sound like a fuse or relay problem.

To check a relay the easiest way is to use a known good relay in place of a potential bad one.

The other possibility is that there is a break on the running light wire somewhere between the front of the truck and the connector at the back. You can use your circuit tester to test the wiring periodically from the front to the back to locate a break and fix as needed.

expert reply by: Michael H