Evacuating And Charging; Gage Calibration; Vacuum System Check; Charging Station Method - GMC G Service Manual

• If less than 88.7 ml (3 ounces), add 88.7 ml (3
ounces) of new oil to system.
• If more than 88.7 ml (3 ounces), add the same
amount of new oil as drained.
• If a new accumulator is installed to system, add
59.1 ml (2 ounces) additional oil to compensate
for that retained by the original accumulator
desiccant.

EVACUATING AND CHARGING

Before charging, evacuate the system if Refrigerant-12
is lost or if the system has been opened.
Evacuation and charging is a combined procedure.
Purge all gage lines with Refrigerant-12 before charging.
There are three standard Refrigerant-12 evacuate and
charge procedures:
• J 23500-01 Charging Station Method
• Disposable Can Method
• Drum Method
NOTICE: Do not use alcohol to remove moisture
from the system . A lcohol can damage
components.

GAGE CALIBRATION

Before evacuation, check the low pressure gage for
proper calibration and the vacuum system for proper opera­
tion. With the gage disconnected from the refrigeration sys­
tem, be sure that the pointer is centered on "0." Tap the
gage to be sure the pointer is not sticking. If necessary,
calibrate as follows:
• Remove the cover from the gage.
• Holding the gage pointer adjusting screw with
one hand, carefully force the pointer in the
proper direction to position the pointer at the "
position. Tap the gage to be sure the pointer is
not sticking. Replace the gage cover.

VACUUM SYSTEM CHECK

Before connecting the vacuum pump to the A/C system,
run the pump connected to the low pressure gage to deter­
mine the vacuum pump capability. If the vacuum system is
unable to reach 711.2 - 736.6 mm (28 to 29 inches) or more
vacuum, check for leaks. If no leaks are found, check the
vacuum pump.

CHARGING STATION METHOD

Follow the J 23500-01 Charging Station instructions.
Use with the following exceptions:
1. Do not connect the high pressure line to the air condi­
tioning system.
2. Keep the high pressure valve on the charging station
closed.
3. Perform the evacuate and charge procedure through
the accumulator low side pressure service fitting.
4. Following these procedures will prevent high side
pressure from damaging the charging station if an
error is made during the sequence.
AIR CONDITIONING IB -27
DISPOSABLE CAN OR
MULTI-CAN METHOD
Tools Required:
J 6271-01 Single Can Refrigerant Dispensing Valve
J 6272-02 Four Can Refrigerant Dispensing Valve
1. Use J 6271-01 for single can or multi-can dispensing
unit.
2. Use J 6272-02 for multi-can open valve. When using
disposable cans, close the tapping valve and^hen
attach the can(s) following the instructions included
with the tapping valve or tapping manifold adapter.

REFRIGERANT DRUM METHOD

Tool required:
J 23390 Refrigerant Dispensing Valve
1. Use J 23390 for a 5.443 kg (12 lb.) can. A 13.608 kg
(30 lb.) can has a built-in opener-valve. Place the
drum on a scale and note weight before charging.
During charging, watch the scale to determine the
amount used.
I { | Important
• Close the outlet valve on the opener (clockwise)
before installing the opener to the R-12
container.
• To evacuate the A/C system install J 23575-01
Manifold Gage Set and Vacuum Pump.
• SLOWLY open high and low side gage valves
and begin vacuum pump operation. Pump the
system until the low side gage reaches 711.2-
736.6 mm (28 to 29 inches of mercury [vac­
uum]) or more.
The evacuation procedure will specify 711.2-
"
0 736.6 mm (28 to 29 inches) of mercury at sea
level. For each 304.8 m (1,000 ft.) above sea
level, lower the specification by one inch of vac­
uum. At 1524 m (5,000 feet) elevation only
584.2-609.6 mm (23 to 24 inches) of vacuum is
required.
If the prescribed mercury (vacuum) cannot be
reached, close the vacuum control valve, shut
off the pump and look for a leak at the connec­
tions or the pump.
2. When the gage reaches the prescribed vacuum, the
system is evacuated. Close the high side gage set
valve and turn OFF the vacuum pump.
3. Watch the low side gage to be sure vacuum holds for
five minutes. If the vacuum holds, disconnect the vac­
uum hose at the gage set and then proceed to
charging.
4. If the vacuum does not hold for five minutes, charge
the system with 0.227 kg.
and leak check. Discharge the system again and
repair any leaks. Repeat the evacuation procedure.

CHARGING THE SYSTEM

1. Start the engine, run with the choke open (if applica­
ble) and the fast idle speed reduced to normal idle.
ounces) Refrigerant-12
(8