Why Are Trailer Running Lights Coming on When Brakes are Applied

Published 09/23/2019

Question:

Trailer 5th wheel clearance lights come on when brakes applied. As title suggests my clearance lights come on when braking, this all happened after installing a 4 point plug at rear ,now all lights work correctly on the secondary trailer . I also tried the trailer on another truck and same problem so that rules out my truck. Where did I go wrong ,all 5th wheel trailer lights work correctly.

asked by: Herman M

Helpful Expert Reply:

You are correct that the issue is on your trailer and based on what you are describing the circuits are somehow swapped when you installed your connector; unfortunately, I was unable to find your order number to see what you purchased from us for the install that may have caused this to happen. It is also possible that the brake and running light circuits shorted out and surged together. Either way, you will need to trace your wiring back, particularly at the running lights to see where any wires are crimped, broken or otherwise damaged. I have also added a link to a help article on wiring troubleshooting which I highly recommend reading.

expert reply by: Kyle S