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Saturday, October 24, 2009

Brake Magnet Polarity

I have a Starcraft RV with dual axles. I noticed that the brake wires on one of the wheels have come loose from the electric brake magnets. Does polarity have to be observed when reattaching these wires? I cannot find any information in the operation and service manuals for the trailer or the axles on wiring to the brake magnets.
David, (San Antonio, TX)


David, brake magnets are direct current (DC) devices. They require positive 12-volts and negative 12-volts (ground connection) in order to become activated. The magnets themselves do not have polarity, but each must have a ground wire and a hot wire in order to complete the circuit powered by the brake controller. That’s why they typically have two wires the same color. So either wire can be attached to either segment of the circuit. Just be sure to attach them both! Hopefully the wires just pulled loose at a connecting point behind the backing plate. This is a fairly common occurrence if the wires are secured without the proper amount of slack. If the wires have pulled out of the magnet itself, it will be necessary to replace that magnet. The leads are connected internally to each of the magnets.

Be sure to use the same size and the same brand if a magnet needs to be replaced. And it is advisable to keep the magnets on each end of the same axle the same age, so if you must replace one, replace the opposite side as well. Oh, and while you’re in there, be sure to check out the brake shoes, the brake drum and armature plate as well as the condition of the springs and actuating lever. Also, check the wheel bearings. Now is a good time to repack them since you’ll have everything disassembled just to gain access to the magnets. This is one area you should bookmark to check regularly.

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