Troubleshooting Tandem Axle Trailer Brakes  

Question:

Expert Reply:

Many brake controllers are rated for 2-8 brake assemblies, which would be 1-4 axles. In any event, I've yet to see the brake controller that shouldn't work fine with a tandem axle trailer using 10 inch brake assemblies, as long as everything is functioning properly.

Which brake controller are you using? Is it throwing any error codes? I'll link to some helpful articles about testing and troubleshooting brake controllers, but I can run through some of the more common and easy to find and fix issues.

• Use a circuit tester like # PTW2993 on the pin in the 5:00 position on the truck's 7-way trailer connector while a helper activates the manual brake switch on the brake controller. You should see power on that pin with the controller's manual brake switch activated. Keep in mind, you won't get output on that pin with the brake pedal from a proportional brake controller unless the vehicle is in motion, but you should get output with the manual brake switch. If you do get power on that pin, then the problem lies in the wiring on the trailer or with the brake magnets themselves. If you don't show power on that pin, check for power on the blue wire in the harness entering the rear of the 7-way while the manual switch is activated. If you still show no power, either the controller is bad (test it as shown in the linked article) or there's a problem with the output circuit between the controller and the 7-way.

• Examine the 7-way connector on the tow vehicle bumper and the connector on the trailer. Are any of the pins damaged? Can you see any green or white corrosion on any of the sockets/pins? If you see any corrosion, there's a chance that it might have spread internally into the connector. You can try cleaning the contacts with fine sandpaper or emery cloth. If anything is damaged, replace it. We offer a replacement connector for the vehicle, part # HM40975-11933. If the connector on the trailer is damaged, I'd recommend the # e99011, which is a combination 7-way connector/junction box.

• Follow the ground connection from the trailer connector, and make sure it's securely connected to the trailer tongue. Make sure the connection isn't corroded.

• Follow the brake output circuit (typically a blue wire) from the trailer connector back to the brake assemblies. Look for loose connections or broken wires. Make sure each brake magnet is securely grounded to the trailer frame and that its connection with the brake output circuit is sound.

• Are your brakes properly adjusted? I've linked to a video showing how this is done. Fast forward to the 4:40 mark, and you can see my buddy Joe showing how brakes are adjusted. If you need a brake adjusting tool, we offer one as part # W80630.

• Once again, with the brake control manual switch activated, use a circuit tester to check for power at the magnets. If you show power there, one or more magnets might be bad. Pull one of the hubs and look at the face of the magnet that rides against the inner armature surface of the brake drum. If you can see any of the interior copper wiring showing through the face of the magnet, it needs to be replaced.

These are the most common things to look for. Running through this list, along with the help articles I've linked, I'm confident you'll be able to locate and correct the problem.

expert reply by: Mike L

0