Troubleshooting Weak Trailer Brake Assemblies After Replacing Magnets

Question:

I have replaced the magnet on 1 wheel of a tandem axle 16foot low-boy trailer. The brakes are not locking up, even at the max. gain setting 10.0 in the truck. I have tested both magnets through resistance and both are in range of 3.4- 3.6 ohms. Could it be a bad ground? I adjusted the brakes to wheel lock and backed off. There is some power getting to the magnets but not enough to lock them up or enough to stop the truck idling in drive. I took the wheels and drums off, hooked up the truck and had a student engage the brake control in the truck. I put a pair of needle-nose pliers on the magnet and was able to pull them off with little force. They were stuck on good, but not so good to were I did not need to pry them off. I hooked another trailer tandem axle cargo trailer with 4 brakes up to my truck. I have a 2014 F-150 with integrated brake control. All four of the wheels locked up at 5.0 gain leading me to believe the truck controller is working great.

asked by: Joe L

Expert Reply:

A weak ground can cause a brake assembly to not be able to totally lock up a trailer wheel. What you will want to do is try running the ground wire back to the main ground wire of the trailer wiring harness. This will give you the best possible ground so that you can know for sure if this is the problem.

Another common problem is brake assemblies that are out of adjustment. You will want the assemblies to be adjusted to the point where there is a light drag on the wheel as you turn it by hand.

Check out the video (see link). Beginning at the 4:23 mark, our installer shows how to adjust your trailer brakes.

expert reply by: Jameson C