I recently bought a new 20' cargo trailer. They checked the brake lights and turn signals before I left the lot and everything appeared to be ok. I didn't physically check the lights.
Recently I scraped the bottom of the trailer at the rear corner and the wiring harness that runs through the ramp door to the tail lights was cut in half. I have a wiring diagram and spent a some time connecting everything back together. Everything works except my brake and turn signal on the left side. Based on the wiring diagram this is the red wire.
I checked the red wire were it was cut in the wiring harness coming from the truck with my multi meter while the hazards were on. Nothing...no voltage. I checked the wire further up just past the 7 pin plug and still nothing...no voltage. I checked the brown wire which runs the right side brake/turn signal at the same spot grounded to the same white ground wire and I got flashing 12v.
My question to the group is where to go next? My thought was to run a 12v battery directly to the red wire just past the plug and see if I get brake lights...that will at least tell me the wire from the plug to the brake light does not have any issues. This will narrow it down to the truck side of the plug or the actual trailer plug.
Any other thoughts? I don't want to haul it back to the dealer.