Troubleshooting Electric Trailer Brakes That Hum But Do Not Engage Drums

Question

Question:

I am trying to get my trailer brakes to work. I can hear a humming sound on the trailer brakes but they arent applying. I dont know what to do cause Ive never worked on electric trailer brakes

asked by: Brady

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Expert Reply:

The humming sound you hear from your trailer's electric drum brakes is a good sign. It means that the brakes' magnets are being energized by the output from the trailer brake controller in the vehicle. The issue with the brakes not applying pressure to the drums could simply be a matter of adjustment, or it could have another cause.

Drum brakes like # AKEBRK-35 have an adjustment device called a star wheel that is located near the bottom of the magnet. Please refer to the picture I prepared for you. Rotating the star wheel upward (as viewed from outside) increases the pressure the brake shows will apply to the drum surface. This wheel can be adjusted with a flat-blade screwdriver or with a brake spoon # W80630. There is a slot in the back of the main plate that allows you to insert the spoon tool.

When a drum brake is adjusted correctly there will be slight drag on the drum when you rotate it by hand. You should be able to hear and feel this drag. Try adjusting your brakes so that they drag slightly on the drum and then test the trailer with your vehicle.

The other possibility is that the brake shoes are worn and this is why there is inadequate pressure on the drums. You can compare the appearance of your brake shoes (specifically their pad thickness) to those on new brakes on our site to see if wear is the issue.

The other possibility is that your trailer brake controller is either set to too low a power level or that it is the proportional type that relies on trailer motion to tell it to generate an output signal. You can set the unit to maximum power and boost and then use the manual override lever to send this full-power signal to your trailer brakes. The brakes definitely should engage when they receive this full-power signal.

You can also refer to the linked articles for more guidance on trailer brakes.

expert reply by: Adam R

0

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Answer 1

First, put the magnet ground wires nearby the magnets on the trailer frame. Running them far away makes it harder for the system to complete the circuit. You mentioned that power is getting to the magnets but how much power? TO determine that you can…

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Answer 2

I'm sure we can get you a hub and drum assembly for your trailer but there's quite a bit of info needed in order to do so. To find the correct hubs you will need to take apart your current hub assembly and look at the bearings themselves;…

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Answer 3

I have a few options for you to help with identifying the correct replacement hubs on your trailer. The first and easiest method would be to crawl under the trailer and look for the axle tag on the beam. This should give an axle capacity which we can…

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Answer 4

That's pretty crazy that you ended up shearing off all 8 of your wheel studs. Normally they will break one at a time but not all together like that. This makes me wonder if maybe you were losing them all one at a time until the last few went out…

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Answer 5

Since the trailer was off of the ground it would not take much voltage to stop the wheels from spinning so they may be getting power but they may not be getting enough power due to a short or wiring issue. But 9 times out of 10 weak trailer brakes…

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Answer 6

Since you mentioned you already tried adjusting your brakes and that did not seem to help, it may be time for new shoes. If enough of the pad has been worn away, they may not be bale to adjust out far enough to make good contact with the drum. If…

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Answer 7

Typically you will not see any voltage on the trailer side of the connector. The 12-volt charge line circuit is generally the only one which will have power depending on if there are diodes in the wiring to prevent power from flowing back through the…

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Answer 8

There are a number of reasons why the brakes on your trailer may not be working. Lets start with the easiest things to check. First, check the vehicle and trailer connectors for corrosion. This can cause a short inside the connector and the brake…

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Answer 9

Thanks for the picture. For your 7,000 lb Lippert axle, I recommend the Electric Trailer Brake Assembly - Self-Adjusting - 12" - Right Hand - 5,200 lbs to 7,000 lbs, #AKEBRK-7R-SA, and for the left side the matching #AKEBRK-7L-SA. These brakes…

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Answer 10

For your application you need the Easy Grease Trailer Hub and Drum Assembly for 3.5K Axles #AKHD-545-35-EZ-K to replace the Tru-Ryde RVD-H-545 trailer hub/drum assembly. This is designed for the industry standard #84 spindle so it uses inner bearing…

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Answer 11

What you described could be a number of things, but testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester…

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Answer 12

For the 2 wires coming off the brake magnet, either wire can be used for either ground or power. You will just want to make sure that the ground wire has a good connection to a clean, corrosion and paint-free location on the trailer frame. A bad…

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Troubleshooting Electric Trailer Brakes That Hum But Do Not Engage Drums

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