Main System Temperature Control Knob
WARNING: This page is about a different car, the 2002 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.
Temperature control knob determines positions of temperature blend door in heater assembly. A potentiometer, operated by temperature control knob, controls movement of temperature blend door via an electric actuator.
Depending on position of temperature control knob, temperature blend door can direct airflow through heater core, around heater core, or through and around heater core for air blending purposes.