WILLIAMS CONTROLSinc. WM764 SERIES DESCRIPTION The WM764 is a panel-mounted three-way control valve that requires actuation both manually and by pilot pressure. The unit consists of two valves—a manually-actuated two-way valve and a pilot pressure-operated three-way valve—that are stacked in series. A white band on the WM764 knob indicates when the valve is actuated. OPERATION The first part of the WM764 valve is a manually-actuated valve that is spring-returned and normally closed. This valve controls the supply port. The second pilot-operated valve controls the exhaust and delivery ports. After manual actuation, the first valve requires a minimum supply pressure of 35-45 PSI (241,3-310,3 kPa) to remain in the open position. When the first valve is manually actuated and no pilot pressure is applied to the second valve, the delivery port is open to the exhaust port. When pilot pressure is applied, the exhaust port closes and air flows from the supply port to the delivery port. If the first valve is manually deactivated when pilot pressure is applied, pressure at the delivery port is exhausted to the atmosphere. If either the supply pressure or the pilot pressure drops below 35-45 PSI (241,3-310,3 kPa), pressure at the delivery port will be automatically released through the exhaust. APPLICATION The WM764 trailer supply valve is engineered for air brake systems of heavy duty tractor-trailer combinations. In the typical installation shown below, the valve controls the flow of air to the trailer parking brakes. The WM764 control valve complies with FMVSS-121. TRAILER SUPPLY VALVE FUNCTIONAL DIAGRAM I.S.O. SYMBOL 119928 REL. 12/79

PARTS IDENTIFICATION DESCRIPTION STEM O-RING STEM BODY POPPET LOCKNUT (114592) O-RING SPRING BODY ASSEMBLY O-RING O-RING LOCKWASHER SCREW BUTTON (117128) SPRING PIN (117071) NUT (117057) SPRING WASHER RECTANGULAR SEAL RETAINING RING SPRING CAP POPPET O-RING SPRING SPOOL COVER [Service this unit with repair kit number 117660. Replaceable items are followed by part numbers. *Asterisk designates parts included in repair kit 117660. *For continuous operation beyond this range, contact factory.