GMC 2009 Yukon XL Owner's Manual page 213

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(Recirculation): Press to turn the recirculation
mode on or off. An indicator light comes on to show that
the recirculation is on.
This mode recirculates and helps to quickly cool the air
inside the vehicle. It can be used to help prevent
outside air and odors from entering the vehicle.
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 also be turned off by turning
off the ignition.
REAR: For vehicles with the rear heat and air
conditioning controls. Press to turn the rear climate
control system on or off. See Rear Air Conditioning and
Heating System and Electronic Climate Controls on
page 3-33.
Rear Window Defogger
The rear window defogger uses a warming grid to
remove fog from the rear window.
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(Rear Window Defogger): Press to turn the rear
window defogger on or off. It automatically turns off
several minutes after it has been activated. The defogger
can also be turned off by turning off the engine. Do not
drive the vehicle until all the windows are clear.
Notice: Do not use a razor blade or sharp object to
clear the inside rear window. Do not adhere anything
to the defogger grid lines in the rear glass. These
actions may damage the rear defogger. Repairs
would not be covered by your warranty.
Heated Mirrors: For vehicles with heated outside
rearview mirrors, the mirrors heat to help clear fog or
frost from the surface of the mirror when the rear window
defog button is pressed. See Outside Power Mirrors
on page 2-50.
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