Buick 1998 Century Owner's Manual page 148

FRONT
This setting directs most of the air
through the defroster and side window vents. Some of
the air goes to the floor ducts and the side window vents.
The air conditioning compressor will run automatically
in this setting unless the outside temperature is below
40°F (4°C). (Even when the compressor is running, you
can control the temperature.)
Air Conditioning
On very hot days, open the windows long enough to let
hot, inside air escape. This reduces the time for the
vehicle to cool down.
For a quick cool-down on very hot days, use MAX with
the temperature knobs all the way in the blue area. If
this setting is used for long periods of time, the air in
your vehicle may become too dry.
For normal cooling on hot days, use NORM with the
temperature knobs in the blue area. The system will
bring in outside air and cool it.
On cool, but sunny days, the sun may warm your upper
body, but your lower body may not be warm enough.
You can use BI-LEV and set the temperature knob to a
comfortable setting. The system will bring in outside air
and direct it to your upper body, while sending slightly
warmed air to your lower body. You may notice this
temperature difference more at some times than others.
Heating
On cold days, use HTR with the temperature knob and
lever all the way in the red area. The system will bring
in outside air, heat it and send it to the floor ducts.
If your vehicle has an engine coolant heater, you can use
it to help your system provide warm air faster when it's
cold outside (0°F (-18°C) or lower). An engine coolant
heater warms the coolant your engine and heating
system use to provide heat. See "Engine Coolant
Heater'' in the Index.
Ventilation
For mild outside temperatures, when little heating or
cooling is needed, use VENT to direct outside
air
through
your vehicle. Your vehicle also has the flow-through
ventilation system described later in this section.
Defogging and Defrosting
Your system has two settings for clearing the front and side
windows. To defrost the windows quickly, use FRONT with
the temperature knob all the way in the red area.
For maximum defroster performance, set both driver and
passenger temperature controls to the warmest setting.
To warm passengers while keeping the windows clear,
use BLEND.