Left Trailer Taillight Malfunctions When Headlights Are Switched On
Question:
Left brake light and turn signal stop working when I turn on the tail lights. Only the right tail light comes on the trailer.
asked by: Phil F
Expert Reply:
What you describe is a classic symptom of a poor ground connection. Everything works fine, until the vehicle headlights or running lights are switched on. When this happens, the maximum amperage load is being drawn which is when a ground problem rears its ugly head.
You'll want to check the ground connection for the trailer connector on the tow vehicle, the main ground on the trailer tongue and the ground connection for each of the trailer taillights. Make sure the ground connection is securely made to clean, bare metal.
This may sound like a simplistic solution, but an insufficient ground connection will cause a trailer taillight system to do all kinds of strange things.
I'll link to an article that has tons of helpful information about troubleshooting trailer wiring.
