Air Handling

All airflow from the blower motor passes through the evaporator core. Based on the climate control panel settings, the temperature door actuator directs airflow through the heater core as needed. The air distribution door actuator controls the airflow to the defrost, footwell or register vents. The air source is from outside air or recirculated passenger compartment air as determined by the air inlet door position.

The air distribution door and temperature door actuators use a potentiometer to sense and communicate the door positions to the HVAC  control module. When an airflow mode, desired temperature or fresh air or recirculation mode is selected the HVAC  control module drives the actuator motor in the direction necessary to make the actuator position agree with the expected HVAC  control module position to be obtained.

The HVAC  control module sends a PWM  signal to the blower motor speed control to control the blower speed. The blower motor speed control provides variable ground feed for the blower motor. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.