System Air Flow

Instrument Panel Ducts:

SYSTEM AIR FLOW
These positions determine the manner in which the system will operate. Each position of the air flow control knob is detented for positive engagement.

OFF
When the air flow control knob is in the OFF position:
- The outside-recirc door is at full vacuum. As a result, outside air is closed off and the recirc air is admitted to the system.
- The defrost door and the floor door are both at full vacuum, closing off the passages to the defrosters.
- The blend door position may be anywhere within the range of its A/C temperature cable travel from full heat to full cold.
- The blower motor is off.
- The panel door is in the no vacuum position.

VENT
When the air flow control knob is in the VENT position:
- The outside-recirc door, with no vacuum being applied, will block recirc air and admit outside air. From there, air flow is directed through the system to the A/C registers.
- The floor door is at no vacuum to block air flow to the floor registers, and the panel and defrost doors are at full vacuum, closing off air flow to the defrosters.
- The temperature control may be adjusted to heat the air, if desired.
- The blower motor is on.

FLOOR
When the air flow control knob is in the FLOOR position:
- The outside-recirc door is in the no vacuum position to block recirc air and admit outside air.
- The floor door is in the vacuum position which closes off all but a minimum of air flow to the defroster.
- The blend air door position will channel air flow so that a desired temperature level will be achieved.
- The panel door is in the no vacuum position to block air circulation to the A/C registers.
- The blower motor is on.
- The defrost door is at full vacuum, closing off air flow to the defroster.

MIX
When the air flow control knob is in the MIX position:
- The outside-recirc, panel, and defrost doors are in the no vacuum position.
- The floor door is in the partial vacuum position.
- The blower motor is on.

DEFROST
When the air flow control knob is in the DEFROST position:
- The outside-recirc air door is in the no vacuum position to block recirc air and to admit outside air.
- Both the floor and the defrost doors are in the no vacuum position so that most of the incoming air is directed to the defroster nozzles. There is a slight air bleed to the floor registers.
- The temperature control knob setting will determine the amount of heat being introduced into the air flow.
- The blower motor is on.

Outside air is drawn into the system from the cowl, through the blower inlet, and into the A/C evaporator/blower motor assembly. It is forced through and/or around the heater core, mixed, and then discharged through outlets in the discharge air duct to the floor area, A/C registers, or through the defroster outlets, depending on the type of climate control desired. Several doors determine the amount of air that goes through the heater core and the particular outlet(s) through which it discharges.