Pontiac FIREBIRD 1972 Service Manual page 28

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HEATING AND VENTILATION
defroster door is positioned to distribute the majority of
the heater system output air flow from the heater outlet
duct with slight air flow from the defroster nozzles. In
DEFROST, the output air flow is distributed just oppo-
site, with the major portion of heater system output air
flow directed toward the windshield.
X SERIES
AIR FAN LEVER
The air-fan lever has two functions; blower speed control
and air inlet control. Moving the lever half way from OFF
toward ON opens the air inlet door to allow outside air to
enter the heater system. Further movement of the AIR-
FAN lever actuates the blower motor at low speed.
Medium and high blower speeds are achieved by further
movement of the lever when more volume of air flow is
desired.
DEFROST LEVER
The defrost lever controls the position of the defroster
door in the heater case. In the OFF position almost all air
flow is directed to the floor from the heater outlet at the
bottom of the heater case (a small amount of air is dis-
tributed from the defroster outlets toward the windshield).
In the DEFROST position the air distribution is reversed
from that in the OFF position. Moving the lever to any
desired point between OFF and DEFROST will divide air
flow between the floor and windshield accordingly.
PLENUM
I
I
Fig. 1-7 B Series Lower Air Vent
TEMPERATURE CONTROL
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ALL
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The temperature lever on the control panel regulates out-
put temperature of the heater by varying the position of
the temperature door. With the temperature lever in
WARM or HOT, all output air from the heater system is
air which has passed through the heater core. Moving the
temperature lever will introduce more air which has by-
passed the heater core until the temperature lever reaches
OFF or COLD and all output air flow is air which has
by-passed the core. This air flow should be very close to
outside air temperature.
VENTILATION
Two lower fresh air vents, one located in each kick pad
(except B Series), are controlled by separate knobs located
on each kick pad. (B Series lower fresh air vents are
located just inboard of the kick pad on either side of the
car, Fig. 1-7). Positioning the vent knobs between full
forward and full out provides ventilation by allowing
regulated amounts of outside air to enter the car through
the vents. Operating the vent knob (pulling out or pushing
in on knob) drives a cable which in turn positions a door
inside the vent to regulate air intake.
B SERIES
In addition to the lower air vents, the B Series has two
other sources of ventilation. When the heater system is
OFF and the ignition switch is in RUN, the blower motor
is operational and outside air is distributed from the purge
opening on the righthand side of the heater case. This
insures an uninterrupted supply of outside air to the in-
terior of the passenger compartment whenever the igni-
tion is ON. (When the heater system is ON, the outside
air is supplied through the heater system.)
Ventilation is also available from two outlets at the center
of the instrument panel, when desired. Regulation of air
distribution from these outlets is controlled by a vent
control panel (Fig. 1-8) on the lefthand side of the instru-
men t panel.
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Fig. 1-8 Vent Control Panel
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B Ser~es