Why Will Fuse Blow When Brakes or Turn Signal is Applied on 2008 Ford F-250 Towing a Trailer  

Question:

Expert Reply:

It sounds as if you have a ground connection issue, or a short on the tail light circuit on the trailer. Most likely it is a bad ground that will need to be found. The bad ground shows up when the tail lights are turned on and the brake or blinker is used because that is when the highest amount of amperage draw is placed on the wiring.

I would start with the trailer connector on the truck and trailer. Open them up and make sure there is no white or green corrosion causing an issue inside the connectors. If so clean them out or replace the connectors with new ones.

If the problem is not found in the connectors, you will need to follow the trailer wiring and check all of the grounds for all of the lights and the trailer connector. Make sure each light is grounded to the trailer frame and that the connection to the trailer frame is free of rust, paint and corrosion. Lights like the Stop, Turn and Tail Light, part # 30-92-001, that you referenced, have a separate ground wire that will need to be checked at the light and the trailer frame. Other lights like running lights down the side of the trailer may have a separate ground wire or they may be grounded through the mounting hardware so you will need to check each of these lights.

While you are checking all of the ground connections, it is a good idea to look at all of the wiring and check for pinched cut or frayed wires that could be causing your issue, or could cause an issue in the future. I am including links to a couple of troubleshooting videos that should help with locating the problem on your trailer.

expert reply by: Jeff D

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