Troubleshooting Brakes on Trailer that Lock up When Trailer Connector is Plugged In

Question:

I hooked up to my trailer over the weekend and immediately when the wiring harness is plugged in, the trailer brakes lock. Unplug the harness, they disengage. I never had an issue with the setup before I have towed it with no problems several times this year and nothing has changed other than the trailer sat for a couple of months. The tow vehicle is a 2016 Dodge Ram V8. Output is reading 0 on the brake post in the truck side of the equation.

asked by: Mike J

Expert Reply:

Sounds like you have a short between the 12 volt power accessory circuit and the brake output circuit on either the trailer or the truck side. Inspect the connectors and wiring looking for any cut or exposed wire and fix as needed. Most likely it's two exposed wires touching each other between those two circuits.

expert reply by: Jameson C