GMC 2002 Sierra - Manual (Page 210)

3-7
(Blend): Airflow is divided equally between the
floor outlet and the windshield defroster outlets. The air
conditioning compressor may run to dehumidify the air
to prevent window fogging.
(Defrost): This setting directs most of the air
through the windshield defroster outlets with airflow
also delivered from the side window and the floor
outlets. When in defrost mode, the air conditioning
compressor may run to dehumidify the air and limit
window fogging.
(Outside Air): Press this button to force the
system to use outside air. Press it again to close off the
outside air.
Pressing the outside air button will cancel the
recirculation button.
(Recirculation): Press this button to limit the
amount of outside air entering your vehicle. This is
helpful when you are trying to limit odors entering your
vehicle or attempting to quickly cool down the interior.
In the AUTO mode, the system will use recirculation as
necessary to cool the air. Pressing the recirculation
button will change the operation to a manual mode and
the air will recirculate non
- stop. Press this button again
to turn off the recirculation feature.
Recirculation may be selected with the fan control in
OFF to limit odors, outside air and dust from entering
your vehicle.
Pressing the recirculation button will cancel the outside
air button.
A/C: Press this button to turn the air conditioning
on and off. The system will cool and dehumidify the air
inside the vehicle when the A/C light is on. When in
AUTO, the A/C is automatically engaged when necessary.
Air conditioning will be automatically disabled when
the outside air temperature drops below a level at which
air conditioning is effective.
Remember that in order for the automatic system to perform
well, it needs A/C to provide cooling performance.