Troubleshooting Trailer Stop/Turn Signals Not Working But Truck Lights Work Fine

Question:

Trailer lights work, no brake lights or turn signal. If I had a blown fuse, the turn Signals wouldn’t work on my truck

asked by: Jimmie B

Expert Reply:

If your tow vehicle is equipped with any kind of factory trailer wiring, there should be fuses under the hood that are dedicated to the trailer signal lights. These would be separate from the tail light circuits on the truck so if one is blown or damaged, it wouldn't necessary affect the truck lights.

If your tow vehicle has factory trailer wiring you can check the owner's manual for the corresponding fuse locations. There should be one dedicated to the trailer's stop/turn signals, which is the one you will want to check.

If your truck isn't equipped with a factory tow package, and your 4-Way or 7-Way runs though the tail light circuits, then you are correct that a blown fuse for this circuit would affect both the trailer and truck lights. If this is the case and you aren't getting running lights on the trailer (but the lights on the truck are working fine) then there could be a ground issue or some damaged wiring that needs to be repaired on the trailer.

Make sure all your ground connections (both on the vehicle and trailer) are attached to clean, bare metal surfaces that are free of any debris or corrosion. Do this also for the individual light assemblies on the trailer, whether they use a dedicated wire or simply ground through their mounting hardware.

If this looks okay try and inspect the stop/turn circuit wires back from the trailer 7-Way to the light assemblies for any exposed, pinched, or otherwise damaged portions that need to be replaced.

If you are still having issues please let me know and we can continue to troubleshoot.

expert reply by: Chris R