Tie Down Engineering Electric Reversing Solenoid Part Number: 11253R Electric reverse lockout solenoid designed for use with hydraulic surge brake actuators equipped with disc brakes. ----------Disc brakes apply full braking force in reverse, so a reversing solenoid is required to prevent the brakes from locking when backing up.-------------This solenoid can be independently wired or connected through a trailer harness equipped with a 5-flat plug.----------- When the tow vehicle is shifted into reverse, the backup circuit energizes the solenoid and prevents hydraulic pressure from applying the disc brakes.------------nowledge Hub: Surge brake disc systems generate full hydraulic pressure even when the trailer is pushed in reverse. -------Without a reverse lockout solenoid, backing up can cause the trailer brakes to fully engage.--------- A properly wired 12V reversing solenoid temporarily blocks hydraulic pressure when the vehicle is in reverse, allowing smooth maneuvering without manual override.