Temperature Control Knob
WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
Temperature control knob regulates temperature of air entering passenger compartment through an electric motor mounted on blend-air door. In cold position, air by-passes heater core to provide maximum cooling.
In other positions, cooled air from evaporator core and heated air from heater core are mixed to provide air of desired temperature. In hot position, A/C system should be off to provide maximum heating.