Pontiac FIREBIRD 1972 Service Manual page 213

1 B-26
1972 PONTIAC SERVICE MANUAL
in the passenger compartment of the car. This tempera-
ture dial serves the same function as the thermostat in
your home. The temperature dial controls the in-car tem-
perature when the selector lever is in the OFF, LO,
AUTO, HI, BILEVEL, or DEFROST positions.
OFF Position
The B Series Automatic Temperature Control System is
completely "shut-off' when the ignition switch of the car
is in the OFF position. When the car ignition switch is
turned on, the electrical circuit to the ATC system is
accomplished. With the control head selector lever in the
OFF position, the system will come on when the engine
water temperature reaches about 120" F. If the tempera-
ture inside the car is above approximately 75"F., the sys-
tem will come on as soon as the ignition switch is turned
on. The fan (blower motor) will run at "lo (purge) blower"
speed and air will flow from the heater outlets (See. Fig.
1B-25). The temperature of the air depends on the control
head temperature dial setting.
VENT Position
When the selector lever is in the VENT position, the
system will come on immediately whenever the ignition
switch is placed in the RUN position. The blower runs at
"lo blower" speed and outside air is distributed into the
passenger compartment of the car through the A/C out-
lets (See Fig. 1B-25).
LO Position
With the control head selector lever in the LO position,
the system will come on immediately if the inside tempera-
ture is or exceeds about 75°F. If inside temperature is
below 75"F., system will come on when the engine water
temperature reaches about 120°F. The blower will then
operate at "lo blower" speed only. Conditioned air will
flow from the A/C outlets, the heater outlets or both when
the system is in "bi-level" operation.
AUTO Position
The operation of the ATC system when the selector lever
is in the AUTO position is the same as the LO position
except that the blower is no longer locked in "lo blower"
operation. The programmer will select any of the four
blower speeds (LO, MED. 1, MED. 2, and HI) in order
to maintain the proper comfort level in the car (See Fig.
1B-25). The system will go into recirculation (recirc.) op-
eration if maximum cooling is required. Recirc. operation
(Max. A/C) is the recirculation of the air from inside the
car through the air conditioning system and back into the
car
A- HEATER OUTLET AIR
B-AIC OUTLET AIR
C-DEFROSTER AIR
*AIR DISTRIBUTION VARIABLE
AIR DISTRIBUTION
POSITION OFF VENT LO AUTO H I BILEVEL DEFROST
Fig. 18-25 Air Flow