Trailer Brakes Only Work with Manual Override with Two Different Trucks

Question:

My trailer brakes are only activating manually on multiple trucks. I still have brake lights when I push my brake pedal, but actual brakes dont work. Recently the plug was changed, but its working the same before AND after the trailer plug switch had to be replaced because someone let it drag on the ground.

asked by: Geneva S

Expert Reply:

If the trailer brakes are not activating with the brake pedal when connected to two different trucks then the common variable is the trailer.

On the trailer side make sure the connector is clean and free of corrosion inside, where the wires attach, and outside on the pins. Trace the brake output wire from the back of the trailer 7-Way (5 o'clock position if looking where the wires attach) and fix any damaged or pinched wires. If you have a breakaway system be sure to check all of its components as well.

At the brake magnets you can check to make sure the grounds are attached to clean bare metal surfaces. If you can see the windings coming through on the magnets they will need to be replaced. You can further test the magnets by following the help article I have linked.

If all of the wiring and the magnets are fine then it is possible that the brakes need to be adjusted out or the output of the brake controller may need to be more aggressive. I have included a couple of additional links on testing and troubleshooting brake controllers if you believe that they could be the issue.

expert reply by: Michael H