Air Handling

There are 5 door actuators that control the air flow into the passenger compartment:

• Defrost vent/register
• Air inlet
• Footwell vent
• Passenger side temperature
• Driver side temperature

All of the door actuators are stepper motors without any feedback circuit or potentiometer. Each actuator has a single voltage circuit for both motor (door) directions which is supplied from the HVAC  control module. Door directional movement is controlled by 4 circuits from the HVAC  control module with a low side driver output. The motor turns or steps through a series of motions to position the actuator door. The HVAC  control module tracks the door actuator positions by counting steps and periodically calibrates itself so it knows how many steps there are for the full range movement. The HVAC  control module sets Diagnostic Trouble Codes (DTCs) by monitoring the current flow through a given movement phase. If it sees too much current it identifies it as a short circuit. If it does not see any current it identifies it as an open circuit.

When an airflow mode, desired driver or passenger temperature, fresh air, or recirculation mode is selected, the HVAC  control module moves the actuator motor in the desired direction.

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