Trailer Running Lights Not Working when Connected to 4-Way on 4 and 7-Way Trailer Connector

Question:

Does the ground wire from trailer need to be ground to trailer? Iv tried it does not seem to matter. My lights work on the round plug but when I use the 4 pin plug brakes light work blinkers work. But if I turn running light on they go out. Running lights dont work at all. The round plug everything works fine. But if I use my little trailer that has 4 pin has this issue.

asked by: Butch

Expert Reply:

The trailer connector you are using on the vehicle needs to be grounded and the connector on the trailer has to be grounded as well. All of the lights also need to be grounded.

This does sound like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H