Running Lights and Marker Lights do not Work on a Boat Trailer with LED and Incandescent Lights  

Question:

Expert Reply:

There are a few different things that could be causing your problem. The fact that some lights are LED and some lights are incandescent should have no effect on their functionality.

The first step I would take is to use a circuit tester, like part # PTW2993, and test the trailer connector on your tow vehicle. With the running lights on, test each pin in your trailer connector for power. If you do not have power for the taillights at the vehicle side trailer connector, then you most likely have a blown fuse if you have factory trailer wiring. If you have an aftermarket wiring harness installed, you will want to check the wiring harness.

If you have power at the trailer connector, then we know the issue is on the trailer. Since the running light, marker lights and ID light are not working, I would suspect a possible short on the running light circuit. All of these lights are powered by the running light circuit. Starting at the trailer connector, work your way toward each light looking for any pinched, frayed or damaged sections of wire. Hot spots for shorts are commonly found around the trailer suspension or anywhere the wiring runs through the frame.

If the wiring looks okay, check the ground connections for each of the lights. The lights should be grounded to a clean bare metal surface of the trailer frame. If your boat trailer has an aluminum frame, I recommend running all of the grounds back to the main trailer ground. Aluminum does not provide the best ground connection and we frequently see ground problems with aluminum trailers.

I have attached an article on trailer wiring that should help when you are troubleshooting your trailer wiring. If you are unable to find the problem or a solution after following these steps, let me know what you come up with and we can take further steps.

expert reply by: John H

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