Trailer Flasher Lights Do Not Work When Running Lights Are On

Question:

Trailer flashers do not work when the running lights are on but work just fine when the running lights are off

asked by: Cody

Expert Reply:

It does sound like a classic ground issue you are having on the trailer since the flashers do not work when the running lights are on but work when they are off. The running lights have a bigger draw on the wiring and if the ground is not sufficient the other lights will not operate properly. I recommend to make sure all of the grounds on your vehicle trailer connector and your trailer are properly grounded to a clean bare metal surface.

Running a ground jumper wire from each light to the main trailer ground normally fixes this as well.

expert reply by: Heather A