Cadillac 1998 DeVille Owner's Manual page 171

To find your comfort zone, start with the
75 "F (24°C)
setting and allow about 30 minutes for the system to
regulate. Press the red or blue temperature buttons
to adjust the temperature if necessary. If you choose
60°F (16"C), the system will remain at that maximum
cooling setting and will not regulate fan speed. If you
choose the temperature of 90°F (32" C), the system will
remain at that maximum heating setting and will not
regulate fan speed. Choosing either maximum setting
will not cause the system to heat or cool any faster.
With the automatic setting, the air conditioning
compressor automatically cycles when needed to cool
the air. In cold weather, when the system senses the
need for heat, the airflow will be directed out the floor
outlets. As the interior temperature approaches a desired
setting, the blower speed will decrease. To maintain
interior comfort, the airflow may move to the instrument
panel air outlets and floor outlets (bi-level mode). On
bright sunny days in cold weather, the airflow may come
out of the air conditioning outlets (AC mode) to
maintain comfort and prevent stuffiness.
If your vehicle is sitting out on a hot day and you have
it set on AUTO, the air will first flow out the floor air
outlets for a few seconds. That is normal. This is to
expel hot air from the air outlets. As the air is cooled,
the airflow will move through the air conditioning
outlets. If you start your vehicle with the fan setting on
HI, it will skip the air conditioning purge.
To avoid blowing cold air in cold weather, the system
w i l l
delay turning on the fan until warm air
is available. The
length of delay depends on the outside
air
temperature,
engine coolant temperature or the time since the engine
was last started. As the coolant warrns up, the blower fan
speed will gradually increase and
air will flow from the
heater outlets, with some airflow to the windshield to
prevent fogging under most normal conditions.
If you leave your vehicle, the system will remember the
control setting the next time you start your engine,
except for recirculation and defrost. Each ignition cycle
cancels recirculation, whereas, DEFROST will change
to automatic operation when the ignition is shut off and
then turned back on.