Troubleshooting Trailer Tail Lights and Turn Signals Malfunctioning When Running Lights Are On

Updated 04/16/2021 | Published 04/14/2021

Question:

Hello, My turn signal and brake lights operate normally or as they should when the running lights are off indicating correct wiring between trailer and truck. But when the running lights are turned on, which all lights on the trailer turn on indicating correct wiring between trailer and truck the brake lights and turn signal no longer operate and the tail lights just stay on solid. Any suggestions as to where to look?

asked by: Terry

Helpful Expert Reply:

I would be happy to help!

Since you are only having issues when multiple functions are trying to work at the same time it is more than likely a ground issue.

I recommend checking the main ground on the tongue of the trailer making sure it is secured to clean rust free metal. If your trailer is a tilt bed or aluminum make sure the grounds from each lights are run to the main ground.

Grounding issues usually cause issues when multiple functions are drawing power at the same time, and can cause all sorts of confusing issues.

I included a link to a helpful article on wiring for you to take a look at.

expert reply by: Samuel C