Air Door Position Sensor / Switch: Description and Operation

Feedback Potentiometer, Blend Air Flap





PURPOSE

The feedback potentiometer, which is located on the top of the heater box, detects the position of the blend air flaps.

OPERATION

The TCC control unit directs movement of the blend air flaps in the appropriate direction, in order to obtain the desired mixture of heated and non-heated air for temperature control. Because the feedback potentiometer is connected by mechanical linkage to the vacuum element and blend air flap linkage, its resistance corresponds to the position of the blend air flaps.
When the feedback potentiometer indicates the correct resistance value which corresponds with the temperature differential (between desired and actual temperature) the control unit halts output to the blend flap vacuum element.
The quality of temperature control depends on the adjustment of the feedback potentiometer, particularly during the cooling mode.