Temperature Control Knob
WARNING: This page is about a different car, the 1995 Ford Probe. However, it is still accessible from the selected car via links, so may be relevant.
A cable connects temperature control knob to temperature blend door. With knob in cool position, air by-passes heater core. With knob in warm position, air is directed through heater core. With knob in intermediate positions, heated air is blended with cooler incoming air to achieve desired temperature.