Defroster Valve and Heater Outlet Valve

The defroster valve and the heater outlet valve are connected together by a mechanical linkage allowing the two valves to move together. The defroster valve and heater outlet valve can be moved to one of three positions. The heater/defroster mode valve vacuum actuator consists of two chambers operated by two vacuum actuators. If no vacuum is applied to either vacuum actuator, the valve is in mid position. Airflow with the valve in the mid position B will be delivered to both the defrost outlets at the windshield and the heater outlets at floor level. When the heater solenoid is activated, vacuum to the defroster valve actuator is supplied by the red vacuum hose and the actuator moves the valve to position C, forcing all airflow to the heater outlets. When the defrost solenoid is activated, vacuum to the defroster valve actuator is supplied by the blue vacuum hose and the actuator moves the valve to position A, forcing all airflow to the defrost outlets.