Pontiac 2004 Bonneville - Manual (Page 154)

Outlet Adjustment
Use the knob located in the center of each outlet to
change the direction of the airflow. Use the thumbwheel
located between the outlets to turn them on and off.
In vehicles equipped with rear seat outlets, you can
adjust the direction of the airflow using the knob in the
center of each outlet. Use the thumbwheel located
between the outlets to turn them on and off.
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