GMC 1999 Sierra 1500 Pickup Owner's Manual page 167

Right Button
Defrost (Top): Press here to operate the defroster. Heated air comes out
near the windshield. You can use it to help clear fog or ice on your
windshield.
Heater (Bottom): Press here, and heated air comes out near the floor. This
setting is best for passenger comfort in cold weather.
The air flow can be blended between the two positions. To blend between
positions, press the side of the button showing the area where you would like
more air flow. The system will automatically begin to blend toward the position
chosen. To stop the system between positions, just press the SAME side of
the button again.
Left Button
Vent (Top): Press the top of this button and all of the airflow will come
through the instrument panel vents.
Heater (Bottom): Press the bottom of this button and all of the airflow will
come through the floor outlet.
The air flow can be blended between the two positions. To blend between
positions, press the side of the switch showing the area where you would like
more air flow. The system will automatically begin to blend toward the position
chosen. To stop the system between positions, just press the SAME side of
the button again.
Temperature Selector Bar
The bar under your system display lets you select the temperature of the air
coming into your vehicle. Press COLD for cooler air and press HOT for
warmer air. Release the bar when the system reaches the temperature you
want. The temperature is shown on the display by an arrow moving between
C and H.
Fan Control Button
This button is in the upper right corner of your system control panel. The fan
has four settings-low, medium low, medium high and high. Press the top of
the button
(t)
to increase the air flow. Press the bottom of the button (-) to
decrease the air flow. The setting you select is shown on your display as
LOW, MED LOW, MED HI
or HI.
Air Recirculation Button
If you press the MAX button (RECIR on some models), the air in your
vehicle will be recirculated. With the air conditioner on, MAX will give you
maximum cooling. It can also be used in all modes to help keep dust out of
your vehicle. When MAX is selected, REC will light on your display.
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