Troubleshooting Trailer Brakes Overheating

Question:

Is it normal for the magnet to have residual magnetism. I had a screwdriver on the magnet and when I released the brake controller the screwdriver was held up. Unplugged the battery and it was still there, unplugged the 7 pin and the screwdriver was still being held up. My brakes have been overheating so I checked the magnet by doing this, is there any reason this would happen? As soon as the screwdriver is removed the magnet is not magnetized anymore though.

asked by: Gabe

Expert Reply:

Yes, it is normal for a brake magnet to have residual magnetism. When a magnet is energized, it creates a strong magnetic field that can induce magnetism in other ferromagnetic materials. When the magnet is de-energized, this induced magnetism can remain in the ferromagnetic material for a period of time (this is residual magnetism). Eventually this dissipates. In your case that happened when you removed the screwdriver from the magnet.

Since your brakes are overheating, I would first make sure they aren't overadjusted. If you spin the wheel with your trailer jacked up there should only be slight resistance. If they are really dragging or not moving then you need to adjust the brakes. If that is not the case then I would check the wiring with a circuit tester like the # PTW2993.

Check the wire at the brake assembly with the 7-way plugged in. If you have power here even though you aren't braking then it is likely there is a short in the wiring or a bad ground. Double check your ground connections and work your way back until you find the short and repair as needed. Make sure when you put your hub and drum assembly back on that you don't overtighten the castle nut. This is another common cause of overheating..

expert reply by: Robin H