TrailBlazer EXT, and Envoy XL

The auxiliary HVAC system provides ventilation for the rear seat occupants.

The auxiliary mode actuator shares a control circuit with the auxiliary air temperature actuator. If change of position is required for both actuators, then the module positions the auxiliary air temperature actuator first. All control circuits for the auxiliary actuators are at a low voltage potential until a change of position is required. The module then applies a high voltage potential to the appropriate control circuit, which will rotate the actuator.