Trailer Lights Malfunctioning On a Dove Tail Trailer When the Brakes Are Activated  

Question:

Expert Reply:

It sounds like you will need to diagnose the problem with a circuit tester, item # PTW2993 if needed, and some physical inspection. I have linked some videos showing how to diagnose wiring problems.

I would start with the trailer connectors. Start on the truck side and check the inside of the connector front and back for corrosion or any loose wires that may be causing the issue. Specifically, check to be sure the taillight circuit terminal, location # 3 in a 7-Way RV connector, does not have the wrong wire connected to it by testing the wire connected there with the circuit tester, and the right turn signal wire is connected to the # 6 terminal, see wiring page link.

Next, check the trailer connector for the same problems and make sure the wires are connected to the correct terminals.

If the connectors are correctly wired and function correctly when checking with a circuit tester, move on to the wiring on the trailer. There is most likely a ground wire that is not making good contact, or a wire that is shorting to ground somewhere. Check the ground wire at the trailer tongue and make sure it is properly connected to the trailer frame and check to be sure each light on the trailer is securely grounded. Check all of the wiring on the trailer to be sure there are no nicks, cuts, or frayed areas causing shorts and bleed over onto other circuits. Be sure to check the power and ground wires for the electric trailer brakes too.

You should be able to locate the issue following these testing procedures. If you still have a problem, let me know what you find and we will work it out from there.

expert reply by: Robert G

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