Why Does Only One Of My Trailer Brakes Lock Up When Driving But All Will Stop When Adjusting Brakes?  

Question:

Expert Reply:

You may have some bad magnets in your brakes. It seems odd that 3 of the 4 would go bad but I have some tests that you can run to determine if they are bad or if the 1 magnet is bad and drawing more power than it should be. The wiring in series in normal for trailer brakes and does not explain why you are having the issue.

The first test you should run is to see what power your brake controller is putting out when your trailer brakes are applied. For this you will need a Multimeter # PT29ZR to check the amperage coming from your brake controller to the trailer brakes. Since your 2018 Winnebago Micro Minnie has four 10" brakes you want to see 15-16.3 amps of power when the controller is set to max and voltage is between 12 and 13 volts. The trailer needs to be connected for this test. If the voltage is higher or lower this tells you that you do have at least one bad magnet or a short in the wiring.

The next test you will be able to test the magnets while they are in the brake hubs. The wiring for each magnet needs to be disconnected before testing. Using the Multimeter you need to test the resistance between the positive and negative wires of the magnet. You should see 3.0-3.8 per magnet. Anything else and the magnet will need replaced.

To test each magnets amperage you will need to disconnect the wiring to each of the magnets again. You will need a separate 12 volt battery source to test this step. You will connect one of the leads from the Multimeter to one of the brake magnet wires and the other Multimeter wire to the positive battery terminal. Finally connect the other wire from the magnet to the negative battery terminal. You should see 3.2-4 amps for each magnet. Anything different the magnet may need replaced.

The final test must be done with the magnets out of the brake assemblies. You can place the base of the magnet on the negative terminal of a 12 volt battery. Then using a Multimeter test for amperage to the wiring. If any amperage is detected the magnet is shorted and needs replaced.

If you find bad magnets they can be replaced with a Replacement Magnet Kit # AKBRKR-M10. But since you have had this issue for some time you may need to inspect the entire brake assembly and replace them if they show excessive wear or heat damage. I recommend the Self-Adjusting Electric Trailer Brake Kit # AKEBRK-35-SA as it save you time on adjusting brakes. This kit includes both the left and right side for one of your 3,500lb axles.

expert reply by: Bud M

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