So I was hauling some slabwood the other day and I noticed the trailer brakes were pulling hard to one side.
Nothing new this trailer gets used and abused and has spent it's whole life outside.
Start by lifting the trailer off all 4 wheels if possible or you can do one wheel at a time. Then pull the breakaway switch on the trailer. If your trailer has an operational power source it does not need hooked up to the truck to work. This will apply voltage to all of the brake axles.
Then try turning each wheel forward by hand within 1/4 of a turn the wheel should stop and you should not be able to hand turn it.
If the wheel continues to turn use a multimeter or test light to verify voltage to the wires going into the back of the drum. If you have no voltage check all of your wiring and your power source. This isn't my area of expertise and I'm not going there.
If you have voltage and the wheel still turns you'll need to remove the outer drum assembly. Most likely the magnet is bad or the ground for the magnet is bad.
Replace the breakaway and disconnect the power source for your safety.
First remove the wheel.
Then remove the dust cap with a large flat screwdriver.
There is usually a cotter pin or some other type of locking device to hold the castle nut on. Remove this the the castle nut itself. You may then remove the outer washer and bearing.
You may now remove the drum. Be careful it's heavy.
Note the inside of the drum. The outer suface should be clean and shiney where the magnet makes contact. If not clean these areas with some sandpaper or scotchbright pad. Be careful to to contaminate the clean bearing area.
You will now see the magnet and brake assembly.
Here's a picture diagram of it.
The way that it works is when voltage is applied to the magnet it attracts to the outer drum surface. That in combination with the drum turning puts pressure on the actuator arm to outward force to both pads.
The most likely cause of your problems is a bad ground from the center of the magnet. Notice all of the rust here.
Push the magnet inward. This will reveal a small clip which holds the magnet to the actuator arm. Use a small screwdriver to carefully remove this clip without damaging it. You will now be able to remove the magnet itself leaving the wires connected.
Notice the small spring on the actuator arm. Don't lose it. You will need to remove it carefully.
Next take a small flat file and clean the inside + area of the center of the magnet. Also clean the actuator arm where the magnet lives. This is the area where your ground fault is occurring. Although the breaks use one wire as a ground it needs the chasis ground in the center of the magnet to operate I cheated and threw the whole magnet in the blast cabinet.
Apply some di-electric or brake caliper grease to the actuator arm and the inside + area of the magnet. Replace the spring and magnet. Push it in and replace the clip. Reconnect your power source and pull the breakaway. The magnet should now be energized. If not you will need to replace it, not very likely.
Now is a good time to give the adjuster a few turns. Replace and spin the drum in between turns being careful not to over tighten. Reinstall your drum. Then the outer bearing, washer, castle nut and cotter pin. Be careful not to over tighten the castle nut. Spin the wheel as you tighten it down. Stop at the first sign of resistance and back off to the next available opening. Over tightening will cause premature bearing wear. Now replace your wheel.
This whole process takes about 30-45 minutes per wheel. It's so simple a male nurse can do it.
Plus you likely saved buying a set of magnets that you didn't need.
