Operating Modes

PURPOSE
Mode Valves
The heater system provides a choice of three basic operating modes consisting of "VENT," "HEATER," and "DEFROST.

OPERATION
Vent Mode
When the mode rotary knob is in the "VENT" position, the defroster valve and heater valve remain closed. As a result, air coming from the instrument panel vents should be nearly the same temperature as the outside air.

Heater Mode
When the mode rotary knob is in the "HEATER" position, the defroster valve remains closed. As a result, air from the blower fan is heated 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 rotary knob is in the "DEFROST" position, 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 maximum airflow to the defroster, with only a small amount of airflow coming out of the heater duct.