Troubleshooting Trailer Brakes that Lock Up when Brakes Are Touched
Question:
I have a 5400 lb boat I trailer. I used the above controller and had no problem trailering it up north. I launched the boat with power off of the trailer. Five days later I went to retrieve my trailer and truck without the boat. I applied the brakes to slow for a turn and the brakes locked. Same thing happened when I applied the brakes in reverse. I disconnected the brakes until I got home to look at it. Today i went out to see if I could find the problem. I noticed that with the trailer attached I put on the brakes and the controller reads from 0 before the brake is applied to an immediate 15. There is no gradual increase in power. I have a dual electric brakes on my trailer. Do I need to replace the controller? Any help would be greatly appreciated.
asked by: Brad
Expert Reply:
Most likely it's a short between a stop/turn circuit and the brake output circuit that is locking up your trailer brakes when the pedal is touched as this is a very common issue. Go over the trailer wiring looking for any obvious shorts like cut or exposed wire and fix/replace as needed. Sometimes the problem is simply corrosion too so you may try cleaning the trailer connector pins as well.
Here's how to fully troubleshoot brake controllers/wiring:
Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the Quickee Tester, part # PTW2993, you should get output to the controller side of the wire you severed. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.
If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire. On the red wire you will only want power when the brake pedal is pressed.
If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.
If these connections check out and the brake controller is properly grounded then there is possibly a problem inside the brake controller.
I am including a link to a video that will show you how to test the wiring on a brake controller.
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