Troubleshooting Trailer Brakes that Lock Up Immediately when Trailer Is Connected

Question:

when any trailer with electric brakes is plug in brakes will not release on the trailer

asked by: Bill B

Expert Reply:

You somehow have a short between the brake output circuit and the 12 volt power circuit. Does the trailer possibly have a 6-way?

There are two accepted methods of wiring a 6-way trailer connector. One method uses the center pin of the connector for the 12-volt accessory circuit, the other uses the center pin for the brake output circuit. If the vehicle is wired using one method, and the trailer is wired the other way, the trailer brakes will immediately receive 12-volts and lock up as soon as the trailer is plugged into the connector.

You can confirm this by using a circuit tester like part # PTW2993 on your 6-way on the truck. Test the center pin and the pin in the 10:00 position to see which pin is hot. Once that is determined, try applying 12-volts to the corresponding pin on the trailer connector using a car battery. If the brakes actuate, then you know the connector on the trailer is wired incorrectly and needs to have the brake output circuit swapped at the connector for the 12-volt accessory circuit.

expert reply by: Jameson C