Function Control (Main)
This function control switch actuates a function selector valve to control vacuum servomotors for floor/defrost door, panel/defrost door and outside/recirculated air door. See Fig 1. When it is in OFF position, function selector switch stops blower motor operation. When in A/C position, function selector switch supplies voltage to A/C compressor clutch and blower motor circuit.
When MAX A/C is selected, recirculation air duct door is at full vacuum, closing off outside air and admitting only recirculated air. See Fig 2. Floor/panel door and floor/defrost door are at full vacuum position, directing airflow to register. Temperature is usually set for maximum cold but may be heated if desired. Air will be picked up at recirculation opening by blower motor. With A/C control set for maximum cold, airflow across evaporator core will be diverted past heater core and then directed into passenger compartment through instrument panel register. There is also some airflow to side window demisters. A/C compressor will be enabled when MAX A/C is selected. Blower motor is on.
When NORM A/C is selected, recirculation air duct door is in no vacuum position, blocking recirculated air and admitting outside air. See Fig 3. Floor/panel door and floor/defrost door are at full vacuum position, directing airflow to instrument panel registers. Temperature may be raised if desired. A/C compressor will be enabled when NORM A/C is selected. Blower motor is on.
When VENT is selected, recirculation air duct door, with no vacuum being applied, will block recirculated air and admit outside air. See Fig 4. From there, air flows through system to instrument panel registers. Floor/panel door is in full vacuum position to block airflow to heater outlet floor duct. Floor/defrost door is at full vacuum, closing off airflow to windshield defroster hose nozzle. There is also some airflow to side window demisters. Temperature can be adjusted to heat air but air cannot be cooled below outside temperature. A/C compressor will be disabled when VENT is selected. Blower motor is on.
When OFF is selected, recirculation air duct door is at full vacuum, closing off outside air and admitting only recirculated air. See Fig 5. Floor/panel door is in no vacuum position, closing passage to instrument panel registers. Floor/defrost door is at full vacuum, closing passages to windshield defroster hose nozzle. Blower motor and A/C compressor are off.
When FLOOR is selected, recirculation air duct door is in no vacuum position, blocking recirculated air and admitting outside air. See Fig 6. Floor/panel door is in no vacuum position, blocking air circulation to instrument panel registers. Floor/defrost door is in full vacuum position, directing all airflow to heater outlet floor duct. Temperature can be adjusted to mix air flowing through and around heater core to achieve desired temperature level. A/C compressor will be disabled when FLOOR is selected. Blower motor is on.
When MIX is selected, recirculation air duct door is in no vacuum position blocking recirculated air and admitting outside air. See Fig 7. Floor/panel door is in no vacuum position, blocking air circulation to instrument panel registers. Floor/defrost door is in partial vacuum position, allowing airflow to both windshield defroster hose nozzle and heater outlet floor duct. There is also some airflow to side window demisters. A/C compressor will be enabled when MIX is selected to dehumidify air and reduce windshield fogging. Blower motor is on.
When DEFROST is selected, recirculation air duct door is in no vacuum position, admitting outside air. See Fig 8. Both floor/defrost door and floor/panel door are in no vacuum position so that most of incoming air is directed to windshield defroster hose nozzle. There is also airflow to side window demisters. Temperature setting will determine amount of air that is directed through heater core and amount that bypasses heater core. A/C compressor will be enabled when DEFROST is selected to dehumidify air and reduce windshield fogging. Blower motor is on.