Troubleshooting a Brake Controller that is Not Activating Trailer Brakes

Updated 03/15/2013 | Published 03/13/2013

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Hook Probe Circuit Tester

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Question:

brake controller in truck reads normal but when i apply brakes with trailer wheel off ground it doesnt stop spinning

asked by: Krk

Expert Reply:

So your brake controller seems to be functioning but the brakes are not applying on your trailer. The first place I would check would be the brake output circuit on the trailer connector that is on your vehicle. You will want to use a circuit tester like the # PTW2993 to test for voltage on this circuit. I attached a video that shows you the idea on how this is done, but you will be testing the brake output circuit for voltage that ramps up while a buddy applies the brakes. I attached a pic of what the 7-way should look like also.

If the voltage looks good there then you know the problem is not on your tow vehicle and is in your trailer wiring.

A lot of times corrosion on the connectors or cut/exposed wires are the culprit. I would check for this on both trailer connectors.

There is also the chance that your brakes could be out of adjustment. Check out the video I attached on trailer brakes that show how this is down. Fast forward to the 4:40 mark to see the adjustment.

Nearly all trailer wiring problems are ground related. I would next recommend you check the grounding of the wires of the brake assemblies and then check the conditions of the brake output circuit wires on your trailer.

I attached an FAQ article on trailer wiring for you to check out also.

expert reply by: Jameson C