Testing Trailer Brake Circuit and Replacing Brake Output Wire on 2013 Ford F-350  

Question:

Helpful Expert Reply:

Since your issue with the trailer brake circuit began with a big bump I would first check the wiring at the 7-way. That bump may have been a pothole but it could also have been a bit of road debris that may have damaged that wire. Essentially you'll want to inspect the truck wiring from the 7-way socket, forward as far as you can trace it.

Look for damage to the insulation, cracks or worn spots. Look for points where the brake wire may be touching suspension components or any sharp edges of the truck frame.

If you can access the brake controller's blue output wire at the back of the controller, you can test it there with a probe tester like # PTW2992. Set the controller for maximum power and boost and press the manual control to generate brake power. Test the output wire to see if the controller itself is sending out the correct output signal.

If there is signal at the back of the controller then you know that it is okay and you probably just have a damaged wire between the controller and the 7-way. In this case it is easy to replace that wire. Use 10-gauge wire # 10-1-1, which is sold by the foot, and butt connectors # 05732-2 to replace the entire brake wire from the back of the controller to the 7-way. This will bypass the original output wire.

I also recommend you use dielectric grease # 11755 on the connections and wire loom # 7509-10 to protect the new brake wire. Zip ties # DW05727-10 can help you secure the loom and wire along the frame.

expert reply by: Adam R

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