Buick 1999 Riviera Owner's Manual page 150

Adjust the direction of airflow by moving the louvered
air outlets.
3-8
You can also adjust the direction of the airflow to the
rear seating area.
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 better, reducing the chance of
fogging 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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