Buick 2007 Rainier Owner's Manual page 174

Defogging and Defrosting
Fog on the inside of windows is a result of high
humidity (moisture) condensing on the cool window
glass. This can be minimized if the climate
control system is used properly. You can use
either defog or front defrost to clear fog or frost
from your windshield.
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(Defog): Use this setting to clear the windows
of fog or moisture. This setting will deliver air
to the floor and windshield outlets.
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(Front Defrost): Press the front defrost button
to clear the windshield and side windows of
frost or fog quickly. The system will automatically
control the fan speed if you select defrost from
AUTO mode. If the outside temperature is
40°F (4°C) or warmer, your air conditioning
compressor will automatically run to help
dehumidify the air and dry the windshield. Do not
drive the vehicle until all the windows are clear.
174
Rear Window Defogger
The rear window defogger uses a warming grid to
remove fog from the rear window.
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(Rear): Press this button to turn the rear
window defogger on or off.
An indicator light in the button will come on to let
you know that the rear window defogger is
activated.
The rear window defogger will turn off
approximately 10 minutes after the button is
pressed. If you need additional warming time,
press the button again.
If equipped, your heated mirrors will also come on
when you press this button.
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.