Sidestepping the Surge
Posted: November 1, 2013
Many surge brake-equipped trailers utilize a reverse solenoid, which automatically disengages the brakes when backing up (eliminating the need for a manual override). The solenoid is tapped into the vehicle’s reverse light system (via the trailer electrical plug). Shifting into reverse energizes the solenoid, which then reroutes the brake fluid back into the reservoir rather than actuating the brakes.
If this is a new problem (i.e., you were able to back up fine before), then the problem could be anything from a corroded or loose connection, a cut or broken “blue” wire (which is the one that activates the solenoid), a blown vehicle fuse (check to make sure you have reverse lights) or possibly a faulty solenoid.
If the backing problem has existed since you had the new brakes installed, it’s possible that the yard used the wrong plug or pin configuration, and the reverse solenoid is not being energized (assuming your trailer has one).
One final thing to consider: While the solenoid operates a valve that shuts off the flow of brake fluid from the actuator to the brakes, in many cases it doesn’t release pressure. As such, when you put your tow vehicle into reverse after stopping, if the trailer brakes were engaged when you stopped, they’ll still be on when you back up (even though the solenoid is energized and the valve is closed). After stopping, ease forward a bit, stop gently (so the brakes don’t engage) and then back up slowly.