Power To Trailer Brake Magnets But Brakes Are Not Engaging

Updated 12/27/2011 | Published 12/26/2011

Products Featured in This Question

Electric Trailer Brake Assembly - Self-Adjusting - 10" - Right Hand - 3,500 lbs

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$50.42

Hook Probe Circuit Tester

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$11.91

Question:

does it matter which lead you connect to the electric brake magnets ...... i have power to them from the blue wire and a ground but they arent working

asked by: Tim N

Expert Reply:

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 ground connection could be causing your problems. You will want to check to make sure each brake assembly has a good ground connection.

If the brake assemblies are not new, you will want to inspect the magnets. If the magnets have windings or wear marks, the magnets are bad and will need to be replaced. You would need to match up your brake assembly size for the correct replacement magnet. You can also test the amperage on your trailer brakes (see FAQ).

Next, I would recommend checking to make sure the brake assemblies are adjusted properly. You will want to turn the adjustment gear which is accessible from the back of the brake assembly (see video link). After making this adjustment you will want to also reset the brake controller. Unplug your brake controller for a few minutes then plug it back in, to make new settings. Then, you will want to drive and engage the brakes using the manual over ride switch on the brake controller to warm the brakes. Warming the brakes will simulate temperatures of brakes when they are in operation. Then you will follow the instructions on your brake controller as if you were first installing the brake controller.

If the problem still persists after checking each brake assembly you will want to work your way up the wiring from the trailer to the brake controller. Begin by inspecting the wires from the brake assembly up to the trailer connector for any cut or frayed wires.

Next, inspect the wires going into the trailer connector. You will also want to inspect the connector for corrosion, if there is corrosion, you will need to replace the connector.

On the vehicle side, inspect the vehicle side 7-way for corrosion. Next, you will want to use a circuit tester like part # PTW2993 to make sure you are getting signal on the 7-way. You will want to have someone to operate the functions while the ignition is in the power accessory mode and the parking brake engaged. Check the pin at the 4 o'clock position while the manual slide lever on the brake controller is activated. If there is not signal, the problem may lie within the vehicle. You will want to make sure that all the wires are ran properly and connected to the brake controller (see brake controller FAQ).

I have linked an FAQ on wiring and a video installation of electric brakes on a trailer.