Troubleshooting Trailer Brakes that Lock Up Randomly on Highway or at Slow Speeds

Question:

Hello my Tekonsha P3 begin locking up my rear brakes at random without touching the break at all this was happening at a complete stop and also while traveling at highway speeds resulting in the trailer brakes locking up for no reason whatsoever at any speed. Someone who is following me said this happened without brake lights coming on as I had thought of an intermittent problem with the brake light switch but that does not appear to be the case. On a recent trip I was forced to disconnect the trailer brake electrical connection because the trailer just kept locking up at any speed and I could not tow any other way I purchase this unit from etrailer last March and it has worked flawlessly until this last trip I disconnected the wiring harness going into the controller and plugged it back in to make sure all connections were okay I did all the connections myself and everything is soldered and properly insulated. And have a past history of doing electrical wiring on automobiles as one of my jobs so everything has been done correctly. The vehicle Im using is a Toyota FJ Cruiser 2008 as I said this unit has performed flawlessly until this last trip and I cant tell you what has happened but I suspect its the controller itself

asked by: Gary C

Helpful Expert Reply:

Does the brake controller display show anything on the display when the brakes lock up? It sounds like you have a short between the 12 volt accessory circuit of your trailer wiring and the brake output circuit which is intermittently locking the brakes up. But if that were the case or if it was any other type of electrical issue you'd most likely see an error message on the screen when it was happening.

With the brake controller unplugged did the problem go away or persist? How is the controller mounted? Is it level side to side and facing the rear of the vehicle?

expert reply by: Jameson C