Pontiac FIREBIRD 1972 Service Manual page 25

1-4 1972 PONTIAC SERVICE MANUAL
Shorted or open blower resistor. Check blower resistor in top of heater case (on
blower and air inlet duct on B Series).
VACUUM SYSTEM DOES NOT OPERATE AIR DOORS
-
G SERIES
CAUSE
Little or no vacuum at door diaphragm.
Leak in vacuum system.
Air door sticking.
Air door does not operate.
Defroster door does not operate.
CAUSE
Blown fuses caused by short in electrical
system.
Front floor mat wet under heater caused by
improperly sealed windshield or
leaking heater core.
Heater "gurgle"
CORRECTION
Check for vacuum leaks or obstruction.
Check vacuum lines for leaks or obstructions.
Check heater control panel vacuum switch.
Replace if necessary.
Check for bind or obstruction at air door.
Check for loose vacuum hose connection
at diaphragm.
Check for loose vacuum hose connection
at diaphragm.
MISCELLANEOUS
CORRECTION
Locate and correct short.
Reseal windshield, or lead-in from radio antenna.
Repair (if possible) or replace heater core.
Check for proper seal to dash and for leak at
hose connection on heater core. Hose leaking
into the heater case is often misdiagnosed as
leaking core.
Check engine coolant level in radiator.
GENERAL DESCRIPTION
Pontiac's heater and defroster system provides rapid the car. Air entering the system is taken through an open-
warm-up and even distribution of warm air to all parts of
ing at the rear of the hood, providing air with a minimum
DEFROSTER
OUTLET
OUTSIDE AIR FROM
COWL PLENUM CHAMBER
HEATER DEFROSTER AIR TEMP
OUTLET DOOR
DOOR DOOR
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Fig. 1-3 Typical Heater Air Flow