Pontiac FIREBIRD 1972 Service Manual page 27

1-6 1972 PONTIAC SERVICE MANUAL
DEFROST
LEVER
TEMPERAT
LEV€ R
AI R-FAN
LEVER
tion approximately 20% of the air flow is directed through
the defroster outlets, 80% through the heater outlets and
the blower motor operation is governed by the fan switch.
Fig. 1-6 X Series Heater Control Panel
Air is directed to the windshield through a duct (defroster
nozzle) running upward from the heater case.
HEATER CONTROL PANEL
B, A and F Series heater controls (Figs. 1-4 and 1-5) are
of the horizontal slide lever design. The levers transmit
motion via bowden cables to the air, defrost and tempera-
ture doors. The G Series control (Fig. 1-5) utilizes vertical
control levers; the temperature lever actuates a cable and
the select lever a vacuum switch.
The X Series heater control (Fig. 1-6) is of the vertical
slide lever design. Three levers trasmit motion via bowden
cables to the air, defrost and temperature doors.
EXCEPT X SERIES
The system selector lever on the heater control panel con-
trols air flow. The fan switch controls blower motor speed.
With the system in the OFF position there is little or no
air flow on A, F and G Series. On the B Series air flow
is controlled by the blower speed switch and all air is
distributed from the purge opening on the righthand side
of the heater case. In the NORMAL or HEATER posi-
NOTE:
On the B Series there is no OFF posi-
tion on the fan switch.
In the DEFROST position on the system selector lever,
approximately 80% of air flow is directed through the
defroster, 20% through heater outlets and the blower mo-
tor operates at speeds governed by the fan switch.
BLOWER CONTROL
Blower speed is controlled by the position of the fan
switch on the control panel. On the B Series the blower
speed range is LO-MED-HI with the blower motor oper-
ating whenever the ignition switch is in the RUN position,
even if the heater control selector lever is in the OFF
position. On all other models, the fan switch range in-
cludes OFF to shut the blower motor off.
AIR CONTROL
The inlet and distribution of air in the heater system are
controlled by the system selector lever on the control
panel. The selector lever positions an air door (all Series)
aild a defroster door (except F Series) by means of bowden
cables (B, A and F Series) or a rotary vacuum valve and
vacuum diaphragms (G Series).
AIR DOOR
The air door is closed on A, G, and F Series when the
control panel selector lever is in OFF and air is prevented
from entering the passenger compartment from the blower
and air inlet duct. On the B Series, the air door closes but
air is not prevented from entering the passenger compart-
ment; all incoming air is directed out of the purge opening
on the righthand side of the heater case.
When the system selector lever is moved to NORMAL
(HEATER on B Series), the air door opens and air is
allowed to pass into the heater case (the B Series purge
opening no longer has air flow). On the F Series, the air
door and defroster door are a single assembly and opening
the air door (NORMAL) not only allows outside air to
enter the heater case but also directs heater output air flow
through the heater outlet duct with a slight flow of air
from the defroster nozzles.
Moving the control panel selector lever to DEFROST will
affect the position of the air door only on the F Series. On
the F Series the air- defroster single door will move to
direct the output air flow from the heater system out
through the defroster nozzles with a slight air flow from
the heater .outlet duct.
DEFROSTER DOOR
-
EXCEPT F SERIES
The defroster door directs the output air flow from the
heater system. In NORMAL (HEATER on B Series), the