Temperature Selector Knob
WARNING: This page is about a different car, the 1996 Ford Ranger and 1996 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The temperature selector actuates a variable resistance switch. This switch varies voltage to an electric actuator used to position temperature blend door.
Positioning temperature selector in any position between full cold setting and full hot setting causes the temperature blend door to direct more or less outside air through or around heater core for whatever proportion of heated or unheated outside air is desired. See Figure. The air blends together as it leaves the heater core and en ters the heater air plenum chamber for distribution.