Troubleshooting Trailer Where Only One Electric Drum Brake Assembly Functions  

Question:

Helpful Expert Reply:

You could have a brake assembly that simply requires adjustment. Some electric drum brakes like Dexter # 23-459 have a Nev-R-Adjust feature that automatically adjusts their tension, but others like # 23-106 have an adjuster mechanism called a star wheel that you need to manually adjust (there's a tool for this, part # W80630) to get the right braking force. The linked photo shows you the location of the star wheel and the included video also calls this out at the 1:20-minute mark. If you can hear humming from the bad brake when you feed it a 12V input signal then this means its getting power and may simply need to be adjusted. I linked a second video showing how to use the adjuster tool; please refer to the 3:00-minute mark in the installation video.

If there is no issue with the brake adjustment you can move on to electrical troubleshooting. Since one of your trailer's electric brake assemblies is operating properly we'll start troubleshooting by checking on the wiring to and the condition of the one bad brake. If the problem were related to the main trailer wiring harness chances are that both brakes would not be working so we'll start off by checking the one bad brake.

First, have a look at the two wires coming off the brake unit. One should be tightly affixed to the trailer frame, to a clean bare metal spot that provides solid metal-to-metal contact, to serve as a ground. Make sure that wire is solidly connected to a clean spot on the trailer frame. If that ground connection is rusty, greasy or loose correct that by cleaning/de-greasing/sanding that ground point. You can re-locate the ground wire to a new spot on the frame is that's easier; you'll just need to drill a new small hole and prepare the surface with sandpaper to remove paint/primer/dirt, etc.

The second wire from the brake should be connected to the trailer's brake circuit wire from the 7-way (or other type of) trailer connector. Trace this wire (often a blue wire is used for trailer brakes) all the way from the trailer plug to the brake unit. Carefully inspect the wire for signs of worn or cracked insulation and repair as needed. If the ground and brake signal wires are okay then you can move on to inspecting the brake magnet.

If the magnet has visible wire showing then it could be worn out. We do offer replacement magnets but an entire new brake is not much more costly than replacement parts so you might want to just use a new brake unit if your magnet is bad. That way you'll avoid the risk of having to replace another part in the near future. I provided a link to our main page for electric drum brakes; you'll just want to match your axle capacity when selecting new left- and right-hand brakes. You also want to make sure the brake diameter and width, and mounting bolt pattern, match yours.

You can also test your magnet for proper operation using a multimeter like # PT89ZR. The linked article describes methods for testing brake magnets and I have linked our page for replacement drum brake magnets if you wish to go this route.

expert reply by: Adam R

1

click to enlarge