1999 Chevrolet Silverado 1500 Pickup Owner's Manual - Page 164

yellowblue RECIRCULATION: Press this button to limit the amount of fresh outside air entering your vehicle. This is helpful when you are trying to limit odors entering your vehicle, because the air inside the vehicle is being recirculated. Pressing RECIRCULATION will recirculate air continuously. RECIRCULATION is used when the fan control is OFF to limit odors, outside air and dust from entering your vehicle. All button lights will go off. The last setting selected will activate when the blower is turned back on. Pressing the RECIRCULATION button will cancel the OUTSIDE AIR button. In the BLEND mode, outside air is forced to reduce window fogging. If the RECIRCULATION button is pressed, the LED indicator will flash three times indicating that forced outside air is activated. The auto recirculation feature will activate when: BLEND: Airflow is delivered through the heater floor outlets, center floor console outlets (if equipped), the windshield defroster outlets and the side window defroster outlets. The air flow can be divided between HEATER and DEFROST depending upon where the knob is placed between the settings. 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, side window defroster outlets and some air through the heater outlets and center floor console outlets (if equipped). If air from the center floor console outlets is not desired or more defroster performance is desired, turn the vents off at the console. When in the DEFROST mode, the air conditioning compressor may run to dehumidify the air to prevent window fogging. OUTSIDE AIR: Press this button to direct the system to use outside air. Pressing the OUTSIDE AIR button will cancel the RECIRCULATION button. D the air conditioning system is activated, D the OUTSIDE AIR button is on, and D the vehicle load is high due to city traffic, extended idling or hot weather. 3-4