My wiring harness went on the passenger side of my tailgate. Auto locks and and wiper stopped working. When I looked the wires in the grey sleeve seem fine however the black ground wire beside it is broken cleanly into two pieces.

Does this also power the third light on the rear windshield?

3 times I have cleaned the bulb contacts, cleaned all the wiring contacts with sand paper and put electric cleaner and dielectric grease on everything in the third brake light. It works fine for a couple of weeks, then it starts flickering and then the warning light stays permanently on and again I have no third light when I step on the brakes. I'm tired of cleaning the contacts and then having it fail again. I'm looking for a long term fix and wondering if it has to do with the passenger side wiring harness?

I hear sometimes the relay under the dash goes and you can solder a wire over 3 of the pins, however I thought this only works on the occasion when your third brake light works fine and you also have a warning light out bulb always on your dash?