2002 Chevrolet Silverado 1500 Pickup Owner's Manual - Page 209

(Blend): Airflow is divided equally between the floor outlet and the windshield defroster outlets. The air conditioning compressor may run to dehumidify the air to prevent window fogging. (Defrost): This setting directs most of the air through the windshield defroster outlets with airflow also delivered from the side window and the floor outlets. When in defrost mode, the air conditioning compressor may run to dehumidify the air and limit window fogging. (Outside Air): Press this button to force the system to use outside air. Press it again to close off the outside air. Pressing the outside air button will cancel the recirculation button. (Recirculation): Press this button to limit the amount of outside air entering your vehicle. This is helpful when you are trying to limit odors entering your vehicle or attempting to quickly cool down the interior. In the AUTO mode, the system will use recirculation as necessary to cool the air. Pressing the recirculation button will change the operation to a manual mode and the air will recirculate non-stop. Press this button again to turn off the recirculation feature. Recirculation may be selected with the fan control in OFF to limit odors, outside air and dust from entering your vehicle. Pressing the recirculation button will cancel the outside air button. A/C: Press this button to turn the air conditioning on and off. The system will cool and dehumidify the air inside the vehicle when the A/C light is on. When in AUTO, the A/C is automatically engaged when necessary. Air conditioning will be automatically disabled when the outside air temperature drops below a level at which air conditioning is effective. Remember that in order for the automatic system to perform well, it needs A/C to provide cooling performance. 3-7