Should a Trailer Brake Magnet Make Contact with a Drum Even With No Brakes Applied

Updated 12/02/2024 | Published 09/08/2011

Products Featured in This Question

Dexter Electric Trailer Brake Assembly - 10" - Right Hand - 3,500 lbs

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$83.92

Hook Probe Circuit Tester

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$12.94

Question:

The brakes work great, but the springs for the magnets hold them against the inside of the drum slightly, just enough so I can hear it, even when the brakes are NOT applied. Is this normal, or should there be an air gap?

asked by: Dan R

Expert Reply:

The magnet should only make contact with the inside of the brake drum when power is applied to the magnet. If it is making contact with the drum all the time, you may have residual power running on the brake wire that is just enough to cause the magnet to grab the drum.

You will need to check the magnet power wire with a circuit tester, # PTW2993, to see if there is any power when the brakes are not applied. If there is, there is a short circuit somewhere and you will need to track it down. Look for loose or broken connections and wires with nicks in them. Also check to make sure the ground wires are attached to a clean metal surface both from the magnets and on the trailer and vehicle side connectors.

Also check for any dirt or corrosion on the inside and outside of the trailer connectors on both the vehicle and trailer side connectors.

You will also want to pull the hub and check for any grooves cut into the drum and wear on the magnet. If the magnet is worn it will need to be replaced. If you see or feel grooves on the inside of the drum it will need to be replaced. I have included an FAQ article that might help with further testing the magnet.

expert reply by: Michael H

John B.

5/17/2020

Why do the little metal clips that hold the magnet in place keep breaking. Every time I pull a drum the metal clips are missing. As you know this will cause the magnet to constantly rub the drum.

Chris R.

5/20/2020

It could be the actuating arm that's causing the break or it might even be the wrong size clips. Is this happening on all of your brake assemblies or just one particular unit? Are the assemblies older?

John B.

5/20/2020

@ChrisR Some older assemblies and some new ones as well. Actually I don't think I have had the drums off since I put a couple of new assemblies on. I am positive that they are the right clips.

Chris R.

5/22/2020

@JohnB I'm honestly not sure why the clips would consistently brake off on your trailer - this isn't really something that we see. I assume you're experiencing normal braking while towing? If not, do the brakes seem overly aggressive or do they ever engage when not actually braking?

Dave

12/2/2024

My 2000lb Dexter electric brake that I just purchased magnet rubs all the time with no wires hooked up - the spring tension on the magnet keeps light pressure on the drum all the time and when energized it grabs - I don’t see any way possible to not have the magnet touching- What am I missing?