GMC 2009 Sierra - Manual (Page 165)

H
(Vent): Air is directed to the instrument panel outlets.
)
(Bi-Level): Air is directed partly to the instrument
panel outlets and to the floor outlets. A little air is
directed towards the windshield and side window outlets.
Cooler air is directed to the upper outlets and warmer
air to the floor outlets.
6
(Floor): Air is directed to the floor outlets, with
some to the windshield, side window outlets, and second
row floor outlets. In this mode, the system will
automatically select outside air.
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(Defog): See “Defogging and Defrosting” later in
this section.
@
(Recirculation): Press this button to turn the
recirculation mode on. When the button is pressed,
an indicator light comes on.
This mode keeps outside air from entering the vehicle.
It can be used to reduce outside air and prevent
odors from entering the vehicle. Recirculation may also
help cool the air inside the vehicle more quickly once
the temperature inside the vehicle is less than the
outside temperature.
The recirculation mode cannot be used with floor,
defog, or defrost modes. If recirculation is selected
with one of those modes, the indicator light flashes
three times and then turns off. The air conditioning
compressor also comes on when this mode is activated.
While in recirculation mode the windows may fog
when the weather is cold and damp. To clear the fog,
select either the defog or defrost mode and increase the
fan speed.
The recirculation mode can be turned off by pressing
the outside air button, or by turning off the ignition.
;
(Outside Air): Press this button to turn on
the outside air mode. When this mode is selected,
air from outside the vehicle circulates throughout the
vehicle. An indicator light on the button comes on
to show that it is activated. The outside air mode can be
used with all modes, but it cannot be used with the
recirculation mode.
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