Travel Trailer Taillights Are Not Working When Running Lights Are Switched On

Question:

Travel trailer turn/hazard lights dont work when truck headlights are turned on.

asked by: Bruce M

Expert Reply:

You will want to use a Test Light # PTW2993 to probe the wires going into your travel trailer. It sounds like the lights were wired in backwards and power wires were reversed. This would cause the brighter filament in your taillight bulb to be on when the running lights are switched on, making it appear as if the bulbs are not working when the headlights are on.

You can test for power going into each taillight wire with the test light to determine if you are getting power to both circuits. If you are the taillight wires are crossed or shorting out to each other. You can verify this by swapping the taillight input wires to see if it resolves the issue. If not you have a short in the wiring. You will need to then trace the wiring looking for where it may be damaged.

This issue could also lie in the wiring and connector for the vehicle or trailer. If you have another trailer you can test the truck to eliminate it or verify the wiring with the test light at the connector on your tow vehicle.

expert reply by: Bud M