Chevrolet 1995 Blazer Owner's Manual page 136

The upper knob changes the air temperature. Turn the knob clockwise for
warmer air. Turn the knob counterclockwise for cooler air.
The lower knob selects the heater
or
air conditioning function and
determines which outlets the air will flow through (instrument panel,
defroster, heater, etc
.).
OFF - This setting turns off all heating functions. Some outside air will
still come out of the heater outlet whenever the vehicle is moving forward.
MAX A/C
-
Air inside your vehicle is recirculated to maximize your air
conditioner's performance and your vehicle's fuel economy. This setting
cools the air the fastest and should be used to keep "unwanted odors" and/or
dust from entering the vehicle.
NORM A/C
-
This setting cools outside air and directs it through the
instrument panel vents. This setting is useful for normal cooling on hot
days.
BI-LEV A/C
-
Air is delivered through the heater floor vents as well as
the instrument panel vents. This setting is useful in cool weather with bright
sunlight.
VENT - Airflow is through the instrument panel vents. Set the upper knob
to the temperature desired. This setting is useful for mild outside
temperatures, when little heating or cooling is desired. The air conditioner
does not run.
HEAT
-
Heated air comes out through the heater floor vents and
windshield defroster vents. This setting is useful for cold weather.
BLEND - Airflow is divided equally between the heater floor vent
and the
windshield defroster vents. This setting is useful in cool weather when you
have fog or ice on the windshield or side windows.
DEF
-
This setting directs most air through the windshield defroster vents
and some through the heater vents. This setting is useful when you have fog
or ice on the windshield.
Engine Coolant Heater (Option)
If you use the optional engine coolant heater before starting your engine,
your heating system will produce warmer air faster, to heat the passenger
compartment in cold weather. See "Engine Coolant Heater" in the Index.
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