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Testing Trailer Brake Magnets

Written by hitchweb Team
Tuesday, February 21, 2012 — 3 Comments

A worn out or faulty brake magnet can impact the trailer's power to stop. While some magnet problems will be noticeable just by looking at your magnet, there may also be electrical problems that can effect performance. An impaired brake magnet can lead to weak or surging brakes, or cause the brakes to pull to one side. It is important to inspect and test the magnets each time the brakes are worked on.

How To Test Trailer Brake Magnets:

Steps for Visual Inspection:

1. If any coil can be seen on the center of the magnet, the magnet is worn out and should be replaced

2. Take a straight edge tool and lay it across the top of the magnet. The edge of the magnet should be parallel to the straight edge all the way across. Any pitting or changes in the magnet's surface indicate abnormal wear and the magnet should be replaced.

3. Inspect the magnet for grease or oil residue, if any is found replace the magnet.


A multimeter that reads amps and ohms will be needed to test trailer brake magnets. The Tekonsha P3 can also be used as it has test functions built in. To test with a multimeter you will connect the ammeter inline with the blue wire exiting the back of the brake controller or use the brake controllers diagnostic readings. If the amperage is greater than the specified amount (see table below), replace the magnet or magnets. If the reading is less than the specified amount, the leads are bad and the magnet or magnets should be replaced.

7" Brake DrumMax Amps at 12-13 Volts
2 Brakes6.3 - 6.8
4 Brakes12.6 - 13.7
6 Brakes19.0 - 20.6
10" & 12" Brake Drums 
2 Brakes7.5 - 8.2
4 Brakes15.0 - 16.3
6 Brakes22.6 - 24.5


Posted in Trailer Parts


Hitchweb Team
Friday, February 9, 2018
Hello Kevin, i'm not entirely sure. You might be best to contact Dexter Axle on this. Please let us know if you require their contact info.
Kevin Reilly
Friday, February 9, 2018
Reworking a 4 wheel trailer for Model A Ford carrier. Can I get by with 1 set of brakes or do I need all r wheels??
Jason Trevino
Wednesday, November 23, 2016
A digital multimeter is good for the test.
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