Power Control Unit

The power control unit is located on bottom side of heater unit. See Figure . The heater control unit consists of a blend-air control motor, potentiometer, adjustment knob, blower motor relays, heater control unit, and linkage for operating blend-air damper.

The heater control unit operates blend-air damper control motor, varying the ratio of cool air to warm air. The opening and closing of the blend-air damper causes the resistance of the potentiometer to change, which in turn is detected by heater control unit. The heater control unit then operates the blend-air damper control motor and servo system in accordance with resistance detected.