Solenoid Valves
BACKING UP WITH DISC BRAKES
Disc brakes will engage immediately when a trailer is backed up. To prevent this, UFP developed an electronic brake fluid pressure relief valve system that is energized from the tow vehicle's back up lights. Brake fluid is routed back to the actuator's master cylinder reservoir, no line pressure builds up and the trailer can easily be backed up. The valve is fail-safe. That is, it will not open if it were to malfunction so the user will always have brakes when towing forward.
Some manufacturers do not use a pressure relieving valve system but rather use a brake fluid blocking valve to save on costs.
UFP DOES NOT RECOMMEND THE USE OF FLUID BLOCKING VALVES.
