Buick 2007 LaCrosse Owner's Manual page 176

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. There are
two modes to clear fog or frost from your
windshield. Use the floor/defog mode to clear the
windows of fog or moisture and warm the
passengers. Use defrost to remove fog or frost
from the windshield more quickly.
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(Floor/Defog): Press this button to direct the
air between the windshield, floor outlets and
side windows. When you select this mode, the
system turns recirculation off and runs the
air conditioning compressor unless the outside
temperature is near or below freezing. Pressing
the recirculation button will have no effect
other than turning on the indicator light while in
floor/defog mode.
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(Defrost): Press this button to direct most of
the air to the windshield, with some air directed to
the side windows. In this mode, the system will
automatically turn off the recirculation and run the
air conditioning compressor, unless the outside
temperature is near or below freezing. Pressing the
recirculation button will have no effect other than
turning on the indicator light while in defrost mode.
Do not drive the vehicle until all windows are clear.
Sensors
The solar sensor on the vehicle monitors the solar
heat and the air inside of the vehicle. This
information is used to maintain the selected
temperature by initiating needed adjustments to the
temperature, the fan speed, and the air delivery
system. The system may also supply cooler air to
the side of the vehicle facing the sun. The
recirculation mode will also be activated, as
necessary. Do not cover the solar sensor located in
the center of the instrument panel, near the
windshield, or the system will not work properly.