Temperature Control Knob
WARNING: This page is about a different car, the 1997 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.
The temperature knob mechanically operates a cable through a cam mechanism to adjust the temperature blend door. Temperature blend door is in the plenum assembly. When temperature knob is in cool position (turned fully counterclockwise), temperature blend door stops airflow to heater core. When knob is in the warm position (turned fully clockwise), air is directed through the heater core. When knob is in intermediate positions, heated air is blended with cooler incoming air to achieve desired temperature.