CVBC

TEST TRACTOR PROTECTION VALVE

*charge the trailer air brake system. (build up normal air pressure and push the "air supply" knob in). shut off the engine. step on and off the brake pedal several times to reduce the air pressure in the tanks. the trailer air supply control (also called the tractor protection valve control) should pop out or go from "normal" to "emergency" position) when the air pressure falls into the pressure range specified by the manufacturer (usually within the range of 20 to 45 psi)

*If the tractor protection valve doesn't work correctly, an air hose or trailer brake leak could drain all the air from the tractor. this would cause the emergency brakes to come on, with possible loss of control.