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Troubleshooting Trailer Wiring that All Stops When Brake Lights Come On


I hooked up my 4 prong trailer plug everything works but brake lights when I hit them all the lights go off on trailer brake lights don’t light up on trailer but light up on my truck.what did I do wrong all wires are color to color


Expert Reply:

What you have in an insufficient ground circuit for your trailer wiring and when you go to use the circuit that draws the most amperage (brake lights) the ground isn't able to keep up which causes all of the lights to shut off. Try improving the connection of the main ground wire of the trailer wiring harness. Make sure it is attached to a clean metal surface. Or you can run all of the trailer wires back to the main ground. This is actually the ideal solution. But you can also check the current grounds for the lights to make sure they are making a solid connection to a clean metal surface.

I attached a couple help article links on trailer wiring troubleshooting for you to check out as well.

expert reply by:
Jameson C

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