HVAC Control Module

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The HVAC control module receives power from two separate sources. The underhood junction block provides keep alive memory (KAM) power through the battery positive circuit. The left instrument panel (I/P) fuse block provides a device on signal to the HVAC control module through the ignition 3 voltage circuit. The ignition 3 voltage circuit also powers the 5 volt regulator. The Class 2 serial data circuit provides a data circuit for scan tool communication and transmit and receive Class 2 messages. Personalization of HVAC operation is not available with this vehicle.

The HVAC control module processes information provided from various air temperature sensors, actuators and driver inputs to ensure that accurate HVAC operation is provided. The HVAC system can work in manual mode and automatic mode. The vehicle operator selects which mode is selected through the HVAC control module switch inputs.

When in automatic mode, blower speed, mode position and air temperature settings are calculated based on the air temperature setting. When in manual mode the blower speed and air delivery mode can be changed. The HVAC control module still tries to maintain the air temperature unless it is set to full cold or full hot temperatures. When at these full extremes the HVAC control module will position the air temperature actuator to its full cold or hot position depending on the selected air temperature.