Chevrolet 2001 Silverado 1500 Pickup Owner's Manual page 191

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.
3-4
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. 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. To return to normal
operation and to prevent stale air, be sure to return
the OUTSIDE AIR.
Between HEATER and 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 and
RECIRCULATION is not available.