GMC 2001 Denali Owner's Manual page 179

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Mode Knob Manual Operation
The right knob on the control panel allows you to
choose the direction of air delivery.
You can choose to set the climate control system
operations yourself, or let the system work for you
by placing the system in AUTO mode. See "Mode
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Knob Automatic Operation" earlier in this section.
VENT: This setting directs most of the air through
the instrument panel outlets and a small amount through
the floor outlets.
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BI LEVEL: This setting delivers air through the
floor outlets as well as the instrument panel outlets.
HEATER: This setting directs most of the
warmed air through the floor outlets and some air
through the windshield defroster outlets.
BLEND: This setting divides airflow equally
between the heater floor outlet and the windshield
defroster outlets. The air conditioning compressor may
run to dehumidify the air to prevent window fogging.
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DEFROST: This setting directs most air through
the windshield defroster outlets and some through the
outlets. The air conditioning compressor may run to
dehumidify the air to prevent window fogging.
OUTSIDE AIR: This setting should be used
for normal system operation and directs the system
to use outside air. Using outside air will limit stale air
odors and help to prevent excessively humid interior air
(from wet boots or clothing or maximum passenger
loads) from being redirected onto windows.
Pressing the outside air button will cancel the
recirculation button.
RECIRCULATION: This setting limits the
amount of outside air entering the vehicle to a very small
amount. This will be helpful to limit odors entering the
vehicle and will assist in reaching comfort in very hot
temperature conditions. Pressing recirculation will cause
the system to recirculate interior air continuously and
may cause the vehicle windows to fog if the passenger
compartment floor is excessively wet.