Mode Selector Knob

The rotary mode selector knob on the heater and A/C control assembly controls the following components:
^ The 2 electrical switches
^ The vacuum valve

The electrical switches activate the following components:
^ The blower
^ The A/C compressor

The vacuum valve supplies or vents the vacuum to the vacuum actuators. The vacuum actuators determine the following conditions:
^ The air intake
^ The discharge locations

By supplying vacuum to the actuators in various combinations, the vacuum valve controls whether the air comes out of the following parts:
^ The floor outlets
^ The panel outlets
^ The defroster outlets

The vacuum valve also controls the following:
^ Whether fresh (outside) air draws into the system
^ Whether inside air recirculates