Friend of mine is having trouble with her trailer's brake lights lighting up only on one side:

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In the above photo, the key is in the ignition, and the vehicle is in park. Not sure, this is an appropriate question here, but there were other wiring related questions, so... Anyway, here is the wiring box setup:


As far as we know, it's a grounding problem. The gray wire with multiple wires coming out is for the disk brakes, and the loose white wire is the ground, but it's just hanging out loose. I'm hoping that someone here will know enough about RV/trailer wiring to spot the problem. Any help is appreciated.


Well, if it was me, I would disconnect all of them and identify the supply wires for brakes, marker etc

Then I would terminate all the wires with ring connectors and put them on the pins in order - with a suitable set of labels.

Once correct operation has been confirmed I would coat with a light coat of a protective spray.

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