Troubleshooting Bad Brake Magnets For Electric Trailer Brakes

Many trailer owners find themselves constantly fine-tuning their electric brake
controller to achieve the desired braking feel when traveling on corrugated roads,
which can prove challenging.

Before beginning, make sure your multimeter is set to amperes and connected to
one of the blue wires on your brake magnet connector plug. Next, loosen and use a
floor jack to raise one wheel that you will be working on.

Threshold Voltage

Mechanical issues with electric trailer brakes like seized lever arms, scored drums or
worn shoes tend to be obvious; however, electrical issues with them may be difficult
to diagnose, including issues like a bad or failing magnet that causes malfunction or
pull to one side of the trailer brakes.

Multimeters are affordable tools that can be used to quickly determine the threshold
voltage of brake magnets as well as identify any electrical faults in towing vehicles.
Simply make sure the engine of your towing vehicle is running, connect its negative
probe to both battery terminal and one of the brake magnet wires and connect its
negative probe’s positive lead with one of them to ensure accurate measurements.

Your multimeter should have an amps setting. Check each wire leading to the brake
magnet and observe its readings; if they show less than 3.6 amps for 7-inch brakes
or 4 amps for 12-inch brakes, your brakes may require replacement as current is not
reaching them and there may be issues with either their controller or wires.

System Amperage

When your brakes don’t work as they should, the problem could lie with either a
broken or worn out magnet, but often lies within your system itself. There are a
couple tests you can perform to isolate this issue: First connect one probe of a
multimeter to the blue wire coming from your trailer connector plug; the second
probe should connect to one of the brake magnet wires. With your car powered on
and trailer brakes activated through either pedal or manual control button on
controller, measure how much current is flowing into magnet wires before
measuring current passing into magnet wires from trailer connector plug blue wire;
find test specs online regarding acceptable amounts.

If your multimeter displays a high reading, this may indicate an issue with either
your wires or controller – check for exposed wires and ensure your breakaway switch
doesn’t short out or melt. If it drops again it could indicate a bad magnet.

Troubleshooting Bad Brake Magnets For Electric Trailer Brakes

Resistance

When activating a trailer brake system, current flows from its controller through
wires to magnets that slide towards a drum and trigger an inner actuating arm to
rotate, pushing against brake shoes to slow the trailer down.

If the magnets aren’t performing as intended, this could indicate that current is not
reaching them; this could point to either wiring issues or a defective controller. To
test for this possibility, loosen lug nuts on one wheel and use a floor jack to lift it
high enough so as to expose brakes.

Set your multimeter to ohms, and connect one probe of its probes to the blue wire
on the connector plug and one probe to the brake magnet’s feed wires. If your
multimeter shows an indication that current is not reaching the magnets, repair or
replace wires and controller as soon as possible.

Loose Wires

If your trailer brakes don’t function despite having been connected correctly to the
car’s controller, this may indicate that current is not making its way from the
connector plug to the brake magnet wires. A multimeter can help identify this; use
its ampere setting and connect one probe from it directly to one of your connector
plug’s blue wires, and the other probe to one of your brake magnet wires for testing purposes.

If the multimeter indicates an internal break in your circuit, you must inspect for
signs of splicing, chafing or broken wire conductors before replacing as necessary.

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