GMC 2007 Yukon XL Owner's Manual page 217

)
(Bi-Level): This mode directs half of the air
to the instrument panel outlets and to the floor
outlets. The flow can be divided between vent and
floor outlets depending upon where the knob is
placed between the settings. 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): This mode directs most of the air to
the floor outlets, with some of the air directed
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 will come on.
This mode keeps outside air from entering the
vehicle. It can be used to reduce outside air and
prevent odors from entering your vehicle.
Recirculation may also help cool the air inside
your vehicle more quickly once the temperature
inside the vehicle is less than the outside
temperature.
The recirculation mode cannot be used with floor,
defrost, or defogging modes. If you try to select
recirculation in one of those modes, the indicator
will flash three times and turn off. The air
conditioning compressor will also come 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.
Recirculation mode can be turned off by pressing
the button again, or turning off the engine.
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