HVAC Control Components
HVAC Control Module
The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain desired air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal. The HVAC control module provides blower, air delivery mode, air temperature settings and input signals to auxiliary HVAC control module. The HVAC system assembly receives power from battery input with ignition 3 voltage circuit as a backup.
The HVAC control module supports the following features:
| Feature | Availability |
|---|---|
| Afterblow | Yes |
| Purge | No |
| Personalization | No |
| Actuator Calibration | Yes |
Auxiliary HVAC Control Module
The auxiliary HVAC control module provides blower, air delivery mode and air temperature settings. When the auxiliary position is selected, from the HVAC control module, inputs from this control assembly will be processed by the Aux. HVAC control module. If equipped with rear seat audio (RSA) the auxiliary HVAC system will support GMLAN.
Front Mode Actuator
The front mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 relay voltage, low reference, control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either, 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer adjustable contact changes the door position with a signal ranging between 0-5 volts.
The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.
Auxiliary Mode Actuator
The auxiliary mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 relay voltage, low reference, control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either, 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer adjustable contact changes the door position with a signal ranging between 0-5 volts.
The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.