Running Lights Do Not Work on Trailer Towed by a 2010 Ford Edge

Question:

I had installed the Curt Wiring Harness Kit #C56160 on my 2010 Ford Edge and everything fit and worked correctly. I always verify that all trailer lights are functioning when using the trailer and noticed the last time that I hooked everything up that the running lights no longer come on. Brake lights and Turn signals function properly but when I turn on my headlights there are no running lights. I used the trailer as it was day time operation and noticed when I stopped for gas that the lights were functioning. At the end of the trip I checked the lights again and the running lights were no longer functioning but all other lights worked properly. I have misplaced my installation instructions so I can not check it for any trouble shooting advice. Can you tell me why this might be happening?

Expert Reply:

This sounds like a classic ground issue that could be the result of a bad or corroded connection, a loose wire, or a dirty/corroded trailer connector. The act of towing the trailer causes some movement and the ground connection changes slightly to where it was working when you had stopped.

What you will want to do is make sure the main ground on the converter on the vehicle is connected to a clean bare metal surface. Verify with a circuit tester like # ALL640595 if needed that the running light signal is making it all the way to the 4-Way on the vehicle.

Check the vehicle and trailer side connectors for any dirt and corrosion and get them cleaned out. On the trailer side, check the main ground on the trailer connector and make sure it is attached to a clean bare metal surface. Then do the same for the running lights.

Also trace the running light wires from the front of the trailer back to each light and look for any nicks with exposed wire. To check for breaks in the wire you will need to use the circuit tester and test the wire at intervals from the front to the back to narrow down where a break might be.

expert reply by:
Michael H

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