Trailer Brakes Lock Up When Connected to Tow Vehicle

Published 08/23/2018

Question:

I am trying to get to the bottom of an issue with my trailer brakes locking when I plug in my truck. First, I realized I took the battery out... could this trigger the brakeaway switch in some way when it is energized by the truck power? The wheels spin fine, but as soon as the truck is connected they lock up and stay locked.

asked by: Matt

Expert Reply:

If the breakaway battery was removed from your trailer then the breakaway switch would become inoperable which means the brakes would not engage if the pin is pulled. Are you by chance using a 6-way trailer connector or any sort of adapter because if so the black battery power connection and the blue brake controller output connection may be reversed. If not there might be a short in the brake output wire (usually blue) that runs for the brake controller in the vehicle back to each braking assembly. This can either be caused by the wire touching another power source or corrosion on the pins inside the trailer connectors. I would first start with the pins inside the trailer connector and then begin to check the wire. If the wire cannot be reached in certain areas it may be best to just run a new one using part # 10-1-1. If you have access to a different tow vehicle and or trailer you can determine if the short is on the vehicle or trailer.

expert reply by: Conner L