Pontiac tempest 1968 Service Manual page 34

CUSTOM A I R C O N D I T I O N I N G
1A-7
described, remove low pressure gauge line at P.O.A.
valve.
2. Crack open high (No. 2) and low (No. 1) pres­
sure control valves on station, and allow refriger­
ant gas to purge from system. Purge slowly enough
so that oil does not escape from system along with
refrigerant.
3. When refrigerant flow nearly stops, connect low
pressure gauge line to P.O.A. valve.
4. Turn on vacuum pump and open vacuum control
valve (No. 3).
5
a
With system purged as above, run pump until
26-28 inches of vacuum is obtained. Continue to run
pump for 15 minutes after the system reaches 26-28
inches vacuum.
NOTE: In all evacuating procedures, the specifi­
cation of 26-28 inches of mercury vacuum is used.
These figures are only attainable at or near sea
level. For each 1000 feet above sea level where
this operation is being performed, the specifica­
tions should be lowered by 1 inch. Example: at
5000 ft. elevation, only 21 to 23 inches vacuum can
normally be obtained.
6. If 26-28 inches vacuum (corrected to sea level)
cannot be obtained, close vacuum control valve
(No. 3) and shut off vacuum pump. Open refrigerant
control valve (No. 4) and allow some refrigerant to
enter system. Locate and repair all leaks.
7. After evacuating for 15 minutes, add 1/2 pound
of refrigerant to system as described in step 6
above. Purge this 1/2 pound and re-evacuate for 15
minutes. This second evacuation is to be certain that
as much contamination is removed from the system
as possible.
8. Only after evacuating as above, system is ready
for charging. Note reading on sight glass of charging
cylinder. If it does not contain a sufficient amount
for a full charge, fill to the proper level.
9. Close low pressure valve on charging station.
Fully open station refrigerant control valve (No. 4)
and allow all liquid refrigerant to enter system.
When full charge of refrigerant has entered system
turn off refrigerant control valve (No. 4) and close
both hand shut-off valves.
10. If full charge of refrigerant will not enter
system, close high pressure control and refrigerant
control valves. Start engine and run at slow idle with
compressor operating. Crack refrigerant control
valve (No. 4) and low pressure control on station.
Watch low side gauge and keep gauge below 50 psi
by regulating refrigerant control valve. Closing
valve will lower pressure. This is to prevent liquid
refrigerant from reaching the compressor while the
compressor is operating. When required charge has
entered system, close refrigerant control valve and
close low pressure control.
11. System is now charged and should be perform­
ance tested before removing gauges.
ADDING REFR1GERANT-12
The following procedure should be used in adding
small amounts of refrigerant that may have been
lost by leaks, or while opening system for servicing
the compressor. Before adding refrigerant to re­
place that lost by leaks, check compressor oil level
and add oil if necessary. See ADDING OIL.
NOTE: This procedure will only apply if the air
inlet temperature is above 70°F. at the condenser.
1. Remove caps from P.O.A. valve and compres­
sor gauge fittings. Attach gauge set to gauge fittings,
making sure Schrader adapter J 5420 is between low
pressure gauge hose and suction gauge fitting, and
J 6163 is between high pressure gauge hose and
discharge gauge fitting.
2. Start engine, turn air conditioning temperature
control knob to full cold position, blower control for
high speed A / C mode. Operate for ten minutes at
2000 rpm to stabilize system.
3. Observe the refrigerant through the glass cover
of receiver-dehydrator with the system operating,
to see if there are any bubbles evident.
a. If no bubbles are evident, then bleed system
slowly through the discharge valve until bubbles
appear in the receiver-dehydrator. Add one pound
of refrigerant as explained under CHARGING THE
SYSTEM.
b. If bubbles are visible in the receiver-
dehydrator with the temperature control knob at
the full cold position and the blower at " H F ; speed,
it indicates partial or complete plug in a line, or a
shortage of refrigerant, or both. Correct condi­
tion. Add refrigerant as explained below until the
sight glass clears, then add another one pound of
refrigerant.
4. Attach flexible hose from center fitting of
gauge set loosely to refrigerant drum or on dis­
posable can valves. Open high and low pressure
valves on the gauge set slightly to purge pressure
gauge lines of air. Tighten fitting of refrigerant
drum or can, when satisfied that all air has been
removed from gauge lines. Close (clockwise) both
hand shut-off valves of gauge set.
5. Partially charge system.
a. Refrigerant-12 Drum Method.
(1) Place pail containing hot water that does