System Airflow

The following illustrations provide vacuum schematics and vacuum control motor charts which illustrate vacuum line routings and air distribution during the various system operating conditions.

Heater and Vent System Airflow Schematic

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

Heater System Vacuum Schematic and Selector Test

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

Function Selector Knob Position	Heater Air Inlet Duct Door	Heater Air Damper Door	Windshield Defroster Door	Blower Motor
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

A pull-pull A/C temperature cable (19988) connects the A/C Air Temperature Control door with the function control knob (18519) in the assembly.

• When the function control knob (SELECT) is in the OFF position, the A/C Air Temperature Control door is positioned to block passage of air to the distribution outlets.

VENT

As the function control knob is moved toward the VENT position, airflow gradually increases to full flow from the panel A/C registers (19893) .

FLOOR

As the function control knob is moved from the panel to the FLOOR position, flow gradually increases to full airflow from the heater outlet floor ducts (18C433) and A/C side window demister and hoses (19E630) .

MIX

When the function control knob is moved from FLOOR to the MIX position:

• The amount of airflow from the heater outlet floor ducts will gradually reduce and the amount of airflow to the windshield defroster hose nozzles (18490) and A/C side window demister and hoses will increase.

DEFROST

With the function control knob in defrost (DEF), the air will be discharged from the windshield defroster hose nozzles onto the windshield glass (03100) and the A/C side window demister and hoses onto the side windows.