GMC 2000 Envoy Owner's Manual page 144

You will find air outlets in the center and on the sides of
your instrument panel.
You can direct the airflow side
thumbwheel located in the center of the vent. The vent
can be tilted up and down also. To control the amount
of airflow through the outlets, rotate the thumbwheel
below the vent.
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to side by rotating the
Ventilation Tips
D
Keep the hood and front air inlet free of ice, snow or
any other obstruction (such as leaves). The heater
and defroster will work far better, reducing the
chance of fogging the inside of your windows.
D
When you enter a vehicle in cold weather, move the
fan control to the right to the highest setting for a
few moments before driving off. This helps clear the
intake ducts of snow and moisture, and reduces the
chance of fogging the inside of your windows.
D
Keep the air path under the front seats clear of
objects. This helps air to circulate throughout
your vehicle.
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