A/C Diagnostic Chart - Pontiac FIREBIRD 1972 Service Manual

CUSTOM AIR CONDITIONING 1A-15
3. Proper evaporator pressure, as controlled by the
conditioning system as well as operation of the air doors.
P.O.A. valve would provide proper freeze protection
for the evaporator.
Check for proper compressor oil level during the repair of
Check and correct all air and refrigerant leaks in the air refrigerant leaks, before conducting an operational test.
INSUFFICIENT HEATING
CONDITION AND CAUSE
Heater outlet temperature too low.
CORRECTION
Check for proper engine thermostat.
Check blower operation.
Inspect TEMP lever and cable for proper operation.
Check heater hoses for function.
On B Series check water control valve
as follows:
1. Start engine and allow to warm up.
2. Set temperature control to full heat.
3. Feel hose from water valve to determine if
water is flowing to heater core. If water is not
flowing, inspect water control valve and vacuum
supply line. (Water should flow
-
no vacuum.)
A/C REFRIGERANT SYSTEM DIAGNOSIS
When trouble shooting the refrigerant system, see Fig.
1A-15 , A/C Diagnostic Chart.
COMPRESSOR DISCHARGE PRESSURE TOO HIGH
CONDITION AND CAUSE
Engine overheated.
Overcharge of refrigerant or air in system.
(Note: Always disconnect thermal
limiter before depressurizing system.)
CORRECTION
See Engine Section.
Systems with excess discharge pressures should
be slowly depressurized at the receiver inlet
connection, observing behavior of high pressure
gauge indicator.
1. Rapid discharge pressure drop indicates air (with
possibility of moisture) in system. When pressure
drop levels but still indicates in excess of
specifications, slowly bleed system
until bubbles appear in sight glass and stop. Add
refrigerant until bubbles clear, then add one-half
pound refrigerant. Recheck operational pressures.
If pressure still remains above specifications
and suction pressure is slightly above normal, a
restriction exists ,in high pressure side of system.
2. Slow discharge pressure drop indicates excessive
refrigerant. If pressures drop to specifications and
sight glass remains clear, stop depressurizing and
recheck operational pressures. If pressures are
satisfactory, depressurize until bubbles appear in
sight glass, stop depressurizing, then add 1/2 pound
refrigerant. Recheck operational pressures.
3. If discharge pressure remains high after
depressurizing system, continue depressurizing
until bubbles appear in sight glass.