System Air Flow

SYSTEM AIR DISTRIBUTION






There are two sources of air available to the air distribution system:
- outside air
- recirculated air

Recirculated air is only used during MAX A/C.

Air distribution within the vehicle is determined by the function selector switch position. Airflow control doors are used to direct airflow within the air plenum chamber. Vacuum control motors are used to position these airflow control doors.

The air distribution system is designed to provide airflow from the defrost nozzle when no vacuum is applied to any of the vacuum control motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak.

Air enters the passenger compartment from the:
- instrument panel A/C register.
- heater outlet floor duct.
- windshield defroster hose nozzle.
- side window demisters.

Passenger compartment air is exhausted from the vehicle through open windows or body air vents.



SYSTEM AIR FLOW DESCRIPTION







MAX A/C
When MAX A/C is selected:
- the heater and A/C air inlet duct door is at full vacuum, closing off outside air and admitting only recirculated air.
- the heater air damper door is at no vacuum, blocking airflow to the heater outlet floor duct.
- the windshield door is at full vacuum, closing off airflow to the windshield defroster hose nozzles.
- temperature control is usually set for maximum cold but may be heated if desired.
- air will be picked up at the recirculation opening by the blower motor. Airflow across the A/C evaporator core will be diverted past the heater core and then directed into the passenger compartment through the instrument panel A/C registers.
- the A/C compressor will be operating when MAX A/C is selected.
- the blower motor is on.







NORM A/C
When NORM A/C is selected:
- the heater and A/C air inlet duct door is set at no vacuum, blocking the recirculation passage and admitting outside air.
- all other door positions are the same as those for the MAX A/C setting.
- temperature settings can be adjusted manually.
- the A/C compressor will be operating.
- the blower motor is on.







VENT
When VENT is selected.
- the heater and A/C air inlet duct door, with no vacuum being applied, will block recirculated air and admit outside air. From there, air flows through the system to the instrument panel A/C registers.
- the heater air damper door is in the no vacuum position to block airflow to the heater outlet floor duct.
- the windshield defroster door is at full vacuum, closing off airflow to the windshield defroster hose nozzle.
- the temperature can be adjusted manually.







OFF
When OFF is selected:
- the heater and A/C air inlet duct door is at full vacuum. As a result, outside air is closed off and recirculated air is admitted to the system.
- the windshield defroster door is at no vacuum and the heater air damper is at full vacuum, closing off the passages to the windshield defroster hose nozzles.
- the blower motor and the A/C compressor are off.







FLOOR
When FLOOR is selected:
- the heater and A/C air inlet duct door is in the no vacuum position, blocking recirculating air and admitting outside air.
- the heater air damper door is in the vacuum position, closing off airflow to the windshield defroster hose nozzle.
- the A/C air temperature control door can be positioned to mix air flowing through the heater core and air from outside to achieve the desired temperature level.
- the windshield defroster door is in the no vacuum position, blocking air circulation to the panel A/C registers.
- the blower motor is on.







MIX
When MIX is selected:
- the heater and A/C air inlet duct door is in the no vacuum position, admitting outside air.
- the windshield defroster door is in the no vacuum position.
- the heater air damper door is in the partial vacuum position, allowing airflow to both heater outlet floor ducts and windshield defroster hose nozzles.
- the A/C compressor operates to dehumidify the air and reduce the windshield fogging.
- the air temperature can be controlled manually.
- the blower motor is on.







DEFROST
When DEFROST is selected:
- the heater and A/C air inlet duct door is in the no vacuum position, admitting outside air.
- both the heater air damper door and the windshield defroster door are in the no vacuum position so that most of the incoming air is directed to the windshield defroster hose nozzles. There is also airflow to the A/C side window demister and hoses.
- the temperature control knob setting will determine the amount of air directed through the heater core.
- the A/C compressor operates to dehumidify the air and reduce windshield fogging.
- the blower motor is on.