Troubleshooting Only Running Lights Work When Trailer Hooked to Truck

Updated 04/16/2024 | Published 04/15/2024

Products Featured in This Question

4-Pole Trailer End Connector

(39)

$7.47

Hook Probe Circuit Tester

(60)

$12.27

Question:

HOOK UP MY TRAILER TO ANOTHER TRUCK AND THE LIGHTS WORKED FINE. MY TRUCK LIGHTS ARE WORKING PROPERLY BUT WHEN I HOOK IT UP TO THE TRAILER ONLY THE RUNNING LIGHTS WORK. WHERE SHOULD I LOOK FOR A PROBLEM?

asked by: MIC R

Expert Reply:

Since the lights work with a different truck the problem is on your truck. Check the connection for debris or corrosion and clean as necessary. After that, I would start testing for power with a circuit tester like # PTW2993. Try testing right behind the connector and work your way back to see if you can find a short. You should also make sure your ground connection is secure.

expert reply by: Robin H