Re: [A/S] Testing brake magnets

["Oliver Filippi" <ofilippi@xxxxxxxxxxxx>]

Ebert,

You can test brake magnets with a good ohm meter.

A single magnet has a resistance of 3 to 3.5 Ohms.

On a dual axle trailer you will have four magnets connected in parallel, so
the combined resistance will drop to 1 Ohm (or slightly less) assuming that
all magnets are electrically sound.

I would first check the resistance of the entire brake circuit.  You can
also actuate all the magnets by pulling the breakaway switch (with the on
board battery connected).  Then listen at each wheel for the hum of the
brake magnet.

Recognize that the condition (wear) of the surface of the magnet which rubs
against the brake drum and the mating brake drum surface is going to have a
significant effect on the effectiveness of the brake system (assuming that
the brake shoes are in good condition and properly adjusted.

Bottom line is that it is impossible to accurately evaluate the condition of
the brakes without pulling the wheel and brake drum.

Oliver Filippi