Trailblazer, Envoy, and Bravada

The auxiliary HVAC system provides ventilation for the rear seat occupants. The rear seat occupants will exercise control of the auxiliary air delivery modes and air speed, while the HVAC control module will maintain control of the air temperature setting. The HVAC control modules blower motor must be ON in order for the auxiliary HVAC system to receive heated or cooled air. The HVAC control module will have the authority to override the auxiliary HVAC system and place it in the OFF mode when a high volume of front defrost air is required. To override the auxiliary HVAC control module, a signal is delivered from the HVAC control module through the class 2 serial data circuit, to the auxiliary HVAC control module. This pause in operation will be indicated by the flashing the text OFF.

When the auxiliary mode switch is toggled, a signal is sent to the auxiliary mode actuator through the auxiliary mode door control circuit. Power and ground are supplied to the auxiliary mode actuator through the ignition 3 voltage and ground circuits.

When the HVAC control module is ON, the air that is delivered to the auxiliary HVAC system is the low auxiliary blower speed. When the operator selects medium blower speed, power is delivered to the auxiliary blower motor through the auxiliary blower motor medium speed control circuit. When the operator selects high blower speed, power is delivered to the auxiliary blower motor through the auxiliary blower motor high speed control circuit. Ground is provided to the blower motor through the ground circuit. Power and ground are provided to the auxiliary HVAC control module through the ignition 3 voltage and ground circuits.