System Air Flow Description

The following illustrations show the effects of the function selector knob (18519) setting on air distribution.

System Airflow Schematic (MAX A/C, NORM A/C, FLOOR)  

Item	Part Number	Description
1	—	Heater Air Damper Door (Part of 18454)
2	18476	Heater Core
3	19805	A/C Blower Motor
4	19834	A/C Blower Wheel
5	19860	A/C Evaporator Core
6	—	A/C Air Temperature Control Door (Part of 18454)
7	—	Windshield Defroster Door (Part of 19740)

System Airflow Schematic—(VENT, MIX DEFROST)

Item	Part Number	Description
1	—	Heater Air Damper Door (Part of 18454)
2	18476	Heater Core
3	19805	A/C Blower Motor
4	19834	A/C Blower Wheel
5	19860	A/C Evaporator Core
6	—	A/C Air Temperature Control Door (Part of 18454)
7	—	Windshield Defroster Door (Part of 19740)

A/C-Heater System Vacuum Control Diagram

Item	Part Number	Description
1	—	Heater Air Damper Door (Part of 18454)
2	18476	Heater Core
3	19860	A/C Evaporator Core
4	19805	A/C Blower Motor
5	19834	A/C Blower Wheel
6	—	A/C Air Temperature Control Door (Part of 18454)
7	—	Windshield Defroster Door (Part of 19740)
8	18A318	Vacuum Control Motor

Vacuum Control Chart 

Function Selector Knob Position	Heater and A/C Air Inlet Duct Door	Heater Air Damper Door	Windshield Defroster Door	A/C Blower Motor
MAX A/C	V	NV	V	ON
NORM A/C	NV	NV	V	ON
VENT	NV	NV	V	ON
OFF	V	V	NV	OFF
FLOOR	NV	V	NV	ON
MIX	NV	NV	NV	ON
DEFROST	NV	NV	NV	ON
VACUUM HOSE COLOR CODE	WHITE	RED/BLUE	YELLOW	—

NOTE: When vacuum is applied to both floor-defrost vacuum lines (red/blue), a full vacuum condition exists. WHEN APPLIED TO BLUE LINE ONLY, PARTIAL VACUUM EXISTS.

OFF

The heater and A/C air inlet duct is closed to outside air.

• The heater air damper door is in the full-vacuum position.
• Windshield defroster door is in the full vacuum position.
• A/C blower motor is OFF.

MAX A/C

• The heater and A/C air inlet duct door is closed to outside air.
• Air from the passenger compartment is drawn through the recirc opening and blown across the A/C evaporator core (19860) .
• From there, it flows past doors closed to the floor and defroster outlets and out through the instrument panel (04320) .

NORM A/C

Airflow follows the same course as MAX A/C except the heater and A/C air inlet duct door is set to draw outside instead of recirculated air through the system.

VENT

Outside air (heater and A/C air inlet duct door closed) is drawn into the system and blown past the A/C evaporator core .

• Depending on the A/C air temperature control door setting, air then bypasses the heater core (18476) when the cable-operated A/C air temperature control door is closed at the opening to the heater core .
• With the A/C air temperature control door closed at the heater core , air is directed past the closed heater air damper door.
• In the VENT position, the windshield defroster door is closed by vacuum to the windshield defroster hose nozzle (18490).
• Air then flows through the panel outlet and ducts to the instrument panel A/C register (19893) .

FLOOR

Outside air is drawn into the system and blown past the A/C evaporator core . From there, it passes through the heater core .

• Vacuum closes the heater air damper door to the windshield defroster hose nozzle and opens it to the floor outlet.
• When the knob is in the FLOOR position, air is also fed to the A/C side window demister and hoses (19E630) .

MIX

With the function selector knob set in the MIX position, the heater air damper door receives partial vacuum.

• As a result, the heater air damper door opens midway to allow airflow to the floor and A/C side window demister and hoses , as well as to the windshield defroster hose nozzle and A/C side window demister and hoses .
• The windshield defroster door, with no vacuum applied, closes the outlet to the instrument panel.
• Airflow begins with outside air drawn into the system and past the A/C evaporator core .
• The cable-operated A/C air temperature control door setting determines how much of the total air input is heated by the A/C evaporator core and how much bypasses the A/C evaporator core .
• The blended air then flows through the partial openings to the floor and windshield defroster hose nozzles.

DEFROST

When the function selector knob is turned to the DEFROST position, all vacuum to the system is cut off. As a result, temperature blending is the only variable which can be introduced into the system.

• Outside air flows past the A/C evaporator core , through and/or bypassing the heater core , and out through the windshield defroster hose nozzle and A/C side window demister and hose outlets.
• Whenever there is a vacuum malfunction in the system, regardless of the function selector knob setting, operation automatically diverts to "defroster only" operation with heat intensity contingent upon temperature knob (A/C air temperature control door) setting.