Trailer Brakes Immediately Lock When Trailer Is Plugged in to Tow Vehicle  

Question:

Expert Reply:

I have a suspicion of what might be happening. Does the trailer have a 6-way trailer connector, and you're using a 7-way to 6-way adapter? If that's the case, there are two accepted ways of wiring a 7-to 6-way adapter. One uses the center pin as the 12-volt power supply, the other uses the center pin as the brake output circuit. So, if the trailer's wired one way, and the adapter's wired the other, it will result in the trailer brakes immediately being applied as soon as the trailer is plugged in to the truck. Use a universal adapter like the # 47549 that allows you to swap the wires for the center pin.

Another possibility is that the trailer connector on the vehicle or the trailer is damaged or corroded. Corrosion can collect on the terminals where the wires connect, and if this gets severe enough, it can allow voltage to bleed from an adjacent or nearby circuit.

If you aren't using an adapter, and the connector on the vehicle and on the trailer isn't damaged or corroded, get back with me and we'll look into some other, less likely possibilities.

expert reply by: Mike L

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