Function Selector Knob
Function selector knob can be placed in OFF, panel, panel/floor, floor, floor/defrost or defrost position. Function selector knob operates a vacuum switch connected to appropriate actuator motors, which operate floor/defrost and panel doors.
Outside/recirculation door is controlled by a vacuum valve and vacuum motor. When function selector knob is in OFF position, vacuum is applied to outside/recirculation door vacuum motor to shut off outside airflow. When function selector knob is in any other position, vacuum is not applied to outside/recirculation door vacuum motor and outside air is allowed to enter vehicle.
When function selector knob is in panel position, air inlet blend door, with no vacuum being applied, blocks recirculated air and allows in outside air. See Fig 1. Air flows through system to driver, passenger and center registers. Vent/register blend door is at partial vacuum to direct airflow to driver, passenger and center registers. Defrost blend is at full vacuum and defrost airflow door is at no vacuum, closing off airflow to windshield defroster nozzles and footwell ducts. Temperature setting can be changed manually to heat air but air cannot be cooled below outside temperature. Blower motor is on.
When function selector knob is in off position, air inlet blend door is at full vacuum, closing off outside air and allowing only recirculated air. See Fig 2. Vent/register blend door is at no vacuum and defrost, footwell and blend airflow doors are at no vacuum, closing off passages to driver, passenger and center registers. Blower motor is off.
When function selector knob is in panel/floor position, air inlet blend door is set at no vacuum, blocking recirculation passage and allowing outside air. See Fig 3. Footwell blend door is in full vacuum position, and panel airflow door is in full vacuum position allowing airflow to blend between panel vents and footwell ducts. Defrost airflow door is at full vacuum, closing off airflow to windshield defroster hose nozzle and directing airflow to heater outlet footwell duct. Blower motor is on.
When function selector knob is in floor position, air inlet blend door is in no vacuum position, blocking recirculation air and allowing in outside air. See Fig 4. Footwell airflow door is at full vacuum position, opening door and allowing airflow through footwell ducts. Defrost airflow door and vent/register blend door are in no vacuum position, closing off airflow to windshield defroster hose nozzles and driver, passenger and center registers. Temperature control can be positioned to mix air flowing through and around heater core to achieve selected temperature level. Blower motor is on.
When function selector knob is in floor/defrost position, air inlet blend door is in no vacuum position blocking recirculation air and allowing outside air. See Fig 5. Footwell blend door is at full vacuum allowing air to flow through footwell ducts. Defrost blend door is in no vacuum position, allowing airflow to both windshield defroster hose nozzle and side window demister hose nozzle ducts. Vent/register blend door is in no vacuum position. Blower motor is on.
When function selector knob is in defrost position, air inlet blend door is in no vacuum position, allowing outside air. See Fig 6. Defrost blend door is at no vacuum, directing airflow to windshield through defroster ducts and side windows through demister ducts. Panel airflow door and footwell airflow 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 demister and hose. Temperature control knob setting will determine amount of air that is directed through heater core and amount that bypasses heater core. Blower motor is on.