Chevrolet Silverado Classic 2007 Owner's Manual page 239

In order to prevent false temperature readings
at startup, the displayed temperature will not
change until the following occurs:
•
Vehicle speed is above 10 mph (16 km/h)
for 5 minutes.
•
Vehicle speed is above 32 mph (51 km/h)
for 2 and a half minutes.
The climate control system uses the information
from these sensors to maintain your comfort
setting by adjusting the outlet temperature,
fan speed, and the air delivery mode. The
system may also supply cooler air to the side
of the vehicle facing the sun. The recirculation
mode will also be used as needed to maintain
cool outlet temperatures.
Defogging and Defrosting
You can use either defog or front defrost to
clear fog or frost from your windshield. Use
the defog mode to clear the windows of fog or
moisture. Use the front defrost button to defrost
the front windshield.
-
(Defog): Use this setting to clear the windows
of fog or moisture. Press the mode button to
select this setting. This setting will deliver air to
the floor and windshield outlets.
0
(Front Defrost): Press the front defrost
button to defrost the windshield. 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.
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