Operating Modes

VENT MODE
With the mode lever in the "VENT" position at the extreme lower end of the slot in the dial, the vent control cable holds the vent valve open so it can admit air to the instrument panel outlet duct. Because this air is taken from the airflow that has not passed through the heater core, It is always at the temperature of the air outside the vehicle.

With the temperature lever in the full "COLD" position, the maximum amount of airflow will be delivered through the instrument panel outlet duct. As the temperature lever is moved away from the "COLD" position, airflow from the instrument panel outlet is reduced.


HEATER MODE
When the mode lever is in the "HTR" position, the vent control cable partially closes the vent valve. The defroster valve remains closed. As a result, air from the blower fan is heated as necessary and directed to the defroster valve which sends most of the airflow to the heater duct, with some going to the defroster nozzle.


DEFROST MODE
When the mode lever is in the extreme upper position in the slot, the defroster control cable moves the defroster valve to fully uncover the opening to the defroster nozzle and restrict the opening to the heater duct. This delivers the maximum airflow to the defroster nozzle, with only a little amount of airflow coming out of the heater duct.