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Running Light Fuse Blowing with Trailer Connecter to 2003 GMC Sierra and Tail Light Kit # TL5RK  


when I connect the trailer and turn on the lights the running light fuse blows. This is a 15amp fuse. all of the turn and brake lights work just fine. This is a boat trailer connected to a 2003 GMC Sierra


Expert Reply:

It sounds like there is a short that is causing an overload situation that is in turn causing the fuse to blow. The problem could be in a number of places, but I would start by checking the grounds on the trailer and on the truck. The ground for the trailer side plug should be attached to a clean, corrosion and paint free bare metal surface on the trailer frame. The lights ground through the mounting studs. They, too should be free of corrosion, dirt, and attached to a bare metal surface.

If the truck came with a 4-Way trailer connector, you can check that the ground is working correctly. I have included links to some videos showing how to test the ground. If the 4-Way was added later, make sure that the ground is attached to a clean, corrosion free bare metal surface on the frame.

Another possible problem is with the wiring that comes with the Incandescent Trailer Tail Light Kit, # TL5RK. The wiring coming back from the trailer plug has 5 wires instead of 4. This is because it is a wishbone harness. The running light signal is split at the connector. For the left side, it will be the yellow wire with brown stripe. It will connect to the brown wire on the left tail light. On green wire with brown stripe goes to the right tail light and connects to the brown wire.

Finally, if the trailer has a lot of additional running lights, it could be too much of a power draw which would also cause the fuse to blow and the lights to not work properly.

expert reply by:
Michael H

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