Operating Modes

Mode Valves

The heater system provides a choice of three basic operating modes, "VENT," "HTR" and "DEFROST." In addition the system has a capability to combine, or "BLEND," the features of "HTR" and "DEFROST" operation.

Vent Mode

With the mode knob in the "VENT" position, the vent valve is open so air can flow to the instrument panel outlet ducts.

Heater Mode

When the mode knob is held in the "HTR" position, the vent valve is partially closed. 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 and some to the defroster nozzle.

Blend Mode

As the mode knob is moved into the "BLEND" area, the defroster valve moves to uncover more of the opening to the defroster. As a result, an increasing amount of air flows to the defroster nozzle and a decreasing amount flows to the heater duct.

Defrost Mode

When the mode knob is in the "DEFROST' position, the defroster valve moves 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.