Heat-Defrost Valve

The Heat-Defrost Valve Vacuum Actuator, which controls the Heat-Defrost Valve, is bi-directional. The actuator is operated by two vacuum motors and two vacuum switches. With the Mode Selector in "MAX," "NORM" "B/L," "VENT," or "HTR," vacuum is applied through the LT GREEN hose, moving the Heat-Defrost Valve to position A. All airflow is directed to the Floor and Side Window Outlets Air Outlets with some air bleeding to the Windshield Air Outlets.

The Heat-Defrost Valve Vacuum Actuator has vacuum applied through the BLUE hose with the Mode Selector in Defrost. The Heat-Defrost Valve is then moved to position C and all airflow is directed to the Windshield Air Outlets with some air bleeding to the Floor and Side Window Outlets.

When the Mode Selector is in "OFF" and "BLEND," neither vacuum motor is under vacuum and the Heat-Defrost Valve Vacuum Actuator moves to position B. Air is then directed to both the Floor, Side Window and Windshield Air Outlets.