Recirculation Mode
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
When the recirculation switch is pressed, a signal is sent from the HVAC control module to the recirculation actuator through the recirculation door control circuit. When the logic receives the signal, the recirculation actuator moves into the recirculation mode. This brings air from inside the vehicle instead of fresh air from the outside. Power and ground are provided to the recirculation actuator by the ignition 3 voltage and ground circuit. Recirculation is not available when the HVAC control module is in the defrost position. The recirculation mode will stay on and the LED will illuminate until a non-recirculation mode is selected.