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· Registered
284 Posts
Discussion Starter · #1 ·
Wiring up the electric brakes on my big dump trailer (pulled behind a Ford DIESEL).

Have a draw-tite controller w/digital display.

Hooked up, manual slider all the way over I get a 4.0 on the display, but the brakes won't hold the truck back, or even do anything. I can hear a hummm from the drum/backing plate area.

The backing plate is plastic, and pulling it away reaveals brand new looking shoes, but no movement in the shoes.

New magnets?


· Premium Member
3,840 Posts
The magnet actually is attached to the end of a lever that applies the brakes, much like a parking brake on drum brakes. When the magnet is activated it "attaches" itself to the inside face of the drum (parallel to the tire, not where the brake shoes rub) which, when the drum is turning, pulls the end of the lever in the direction the drum is turning which applies the brakes. As a result you will have minimal to no braking feel when stopped, if the brakes are applied you will have to roll perhaps 1/16 to 1/8 of a turn of the tires to get the brakes activated. This may be part of what you are feeling. It also explains why you do not see any movement in the shoes when you apply the brakes without the trailer at least rolling a little bit forward.

The hum you hear should be the magnets activating. An easy way to tell if the magnets are working is to bring a compass near each drum with the brakes activated. The brake magnets should draw one end of the compass needle to the drum.

Have you tried them rolling in the driveway (forward) or down the road?

Dave / Believer45
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