Buick 1993 Century Owner's Manual page 117

The air conditioner compressor operates in all
AIR COND
positions, and in DEF (Defrost) when the outside
temperature is above about 40°F (4.5" C).
Ventilation
For mild outside temperatures, when little heating or
cooling is needed, slide the upper lever to
V E N T .
Air
flow is through the instrument panel outlets. Rotate the
control next to the outlets to turn on, adjust or turn off
the air flow. Adjust the lower lever on the control panel
to the temperature desired.
Heating
When outside temperatures are cold, sliding the upper
lever to HEATER and the lower lever to HOT will send
heated air through the heater ducts, and some through the
defroster vents. VENT and HEAmR are labeled
ECONOMY positions because the air conditioner
compressor doesn't run in these two settings. This
reduces engine load, resulting in improved he1 economy.
If either setting fails to keep you comfortable, or causes
your windows to fog up, slide the upper lever to one of
the AIR
COND
positions, or to DEF (Defrost).
Defrosting
The DEF setting directs most of the air through the
defroster vents, and some through the heater ducts.
Defogging Windows with Four Season
Climate Control
To quickly defog the windshield, set the upper lever to
DEF and move the
hn switch to
HI.
Slide the lower
lever to HOT.
In
damp, cool weather (temperatures about 45"-65"F,
7"- 18" C), you can use BI-LEV to defog the side windows.
Set the upper lever to BI-LEV and the fan
switch to
HI.
Aim the side vents toward the side windows. For increased
air flow to the side vents, close the center vents.
Rear Window Defogger
(Option)
- -
The rear window defogger
uses a warming grid to
remove fog from the rear
window. In winter, it can
also keep ice from forming
on the rear window.
Press the ON portion of the
switch. The indicator light
will glow. The rear window
defogger will turn off
automatically after about 10
minutes of use. You can
also turn it off by turning
off the ignition or pressing the
OFF
portion of the
switch.