Pontiac FIREBIRD 1972 Service Manual page 26

HEATING AND VENTILATION 1-5
of dust, foreign material and ,undesirable fumes. This air
passes through the plenum chamber into the heater blower
motor and air inlet duct.
The use of outside air provides constant and rapidly
changing air inside the car, eliminating a smoke-filled
interior to keep occupants comfortable.
The driver has fingertip control of the temperature of
warmed air entering the car. When heated air is desired,
the blower forces air taken from the blower and air inlet
duct across the heater core and through an air distribution
system to air outlets inside the passenger compartment
(Fig. 1-3).
The design of the heater and defroster system, its doors
(valves), and controls permits a method of obtaining two
different levels of forced air flow for heating.
All heater systems are composed of the same basic compo-
nents although they may differ slightly in design and
capacity. Hot water is supplied to the heater core by the
engine water pump through a heater hose. Air flow in the
system is initiated in the plenum chamber where outside
air is picked up by the blower motor and directed through
the air inlet duct to the heater case. There, depending on
the control panel setting, air is directed either through or
around the heater core to the outlets. Here again, depend-
ing on control panel settings, air is directed primarily out
the heater outlet to the front floor area or up through the
defroster duct to the windshield area.
The doors which control air flow in the system are moved
mechanically by either vacuum diaphragms or by cables.
Three doors are utilized on all systems except F Series: a
temperature door, an air door and (except F Series) a
defroster door.
Should the system fail to satisfy, proper operation should
be reviewed. This will determine whether the system is
defective or being operated incorrectly.
F A N
I
I
SWITCH
SYSTEM SELECT
/
L E V E R
I
I
TEMPERATURE
/
I
L E V E R
AIR DISTRIBUTION
Heated air enters the interior of the car and is distributed
by a center outlet under the heater duct which dispenses
air over the front floor area and to the rear passenger
compartment. On some models equipped with stereo tape
or console, a different type duct is used which directs the
air to each side of the console or stereo tape unit.
A SERIES
G SERIES
F SERIES
A-SYSTEM SELECTOR L E V E R
0-TEMPERATURE L E V E R
C-FAN SWITCH
Fig. 1-4 B Series Heater Control Panel
Fig. 1-5 Heater Control Panels
-
A,
G and F Series