Mode Knob

The mode knob uses vacuum in order to control the valves that regulate airflow through the heater module. The primary mode knob positions are identified as follows:
^ HTR
^ VENT
^ DEFROST

The intermediate zones between HTR and VENT, or HTR and DEFROST are identified as BLEND. Placing the mode knob in the BLEND position sets the controls to provide a combination of the features of the 2 nearest primary modes.