A/C-Heater System

Manual A/C-heater system functions are controlled by Body Control Module (BCM), except blower motor speed. BCM supplies voltage or ground to components of A/C-heater system for desired Heater, Ventilation & Air Conditioning (HVAC) control panel settings. BCM controls position of recirculation door actuator, mode door actuator and blend door actuator by potentiometer feedback signal for each actuator. Feedback signals allows BCM to know the exact position of each actuator door at all times. BCM also monitors evaporator temperature sensor, and can request Powertrain Control Module (PCM) to disengage compressor clutch when evaporator core temperature is too cold, to prevent icing of evaporator core.

HVAC control panel blower switch is hard wired in series with blower motor through blower motor resistor. See Figure. Blower motor has battery voltage applied whenever ignition switch is in ON or ACCY positions. Blower motor operation and blower motor speeds are controlled by blower switch at HVAC control panel by directing the appropriate path to ground through blower motor resistor. Maximum blower motor speed is achieved by directly grounding blower motor ground circuit.