Troubleshooting Trailer Brakes that Lock Up When Trailer Connector is Connected to Tow Vehicle

Updated 03/21/2016 | Published 03/19/2016

Question:

upon plugging hitch wiring together brakes on trailer apply without using the brake controller

asked by: Frank W

Expert Reply:

Are you using a 6-way trailer wiring connector? Typically when this problem occurs it's when the trailer connector is a 6-way. The reason for that is that there are two common ways to wire up a 6-way and the only difference is that the 12 volt accessory circuit and the brake output circuit is swapped. So this causes the brakes to immediately lock up when connected.

The easy fix is to just cut the wires going to both circuits and swap them.

I attached a wiring diagram that shows a standard 6-way pin out.

expert reply by: Jameson C