Troubleshooting Trailer Brakes that Lock Up When Trailer Wiring is Connected

Published 08/08/2014

Products Featured in This Question

Replacement Trailer Brake Magnet for 12" Brake Assemblies

(41)

$29.03

Hook Probe Circuit Tester

(66)

$14.40

Question:

I just bought my first trailer that came with what I was told was a correctly wired 7 pin connector. I tested it before I bought it and all the lights and turn signals work. The problem is that the brakes lock up when I plug the connector in and they wont un-engage. I though it was because I didnt have a brake controller, but even with one, they wont un-engage. The brake controller even says that there is no connection. The truck side connection is a factory Dodge 2013 so I dont think its on the truck side. Any help would be much appreciated. Thanks!

asked by: Ben

Helpful Expert Reply:

What it sounds like is happening is that the 12 volt accessory circuit on your trailer wiring is being mistakenly wired to the brake output circuit either by a short or something being miswired.

I would first start at the 7-way of your truck and using a circuit tester like part # PTW2993 check for voltage in all of the correct pins. I attached a diagram for you to use as a guide.

Next, you can use a jumper wire from a 12 volt car battery to apply voltage on all of the different circuits of the 7-way on your trailer to see if everything matches. I suspect the problem is on the trailer side. You can also check the back sides of either connector to see if there is any corrosion or exposed wire and fix as necessary.

I attached a couple helpful FAQ articles for you to check out as well.

expert reply by: Jameson C