GMC 1976 ZEO 6083 Maintenance Manual page 75

1- 58 AIR CONDITIONING SYSTEM
c. Temporarily refasten the tool .
d. Reconnect refrigerant line to supply tank .
EVACUATING AND CHARGING
THE SYSTEM
NOTE : In all evacuating procedures shown be-
low, the specification of 28-29 inches of Mercury
vacuum is used . These figures are only attainable
at or near Sea Level Elevation. For each 1000
feet above sea level where this operation is being,
performed, the specifications should be lowered
by 1 inch . Example: at + 5000 ft . elevation, only
23 to 24 inches of vacuum can normally be ob-
tained .
Whenever the air conditioning system is open for
any reason, it should not be put into operation again
until it has been evacuated to remove air and mois-
ture which may have entered the system .
The following procedures are based on the use of
the J-24410 Charging Station :
ADDING OIL
If necessary, refrigeration oil may be added to the
system by the following method :
1 . Install charging station and purge system as
previously described.
2. After system has been purged, connect the
vacuum line to the vacuum pump .
CHARGING STATION
HIGH PRESSURE LINE
TO HIGH
PRESSURE
FITTING
REFRIGERANT
OIL
A-2249
Figure 29-Adding Refrigeration Oil
3. Measure oil loss collected as a result of purging
the system .
a. Disconnect the Charging Station low pres-
sure line . Install Tool J-24095 (with valve closed)
onto the system low pressure fitting. Insert pickup
tube into graduated container of clean refrigerant oil
(figure 29).
NOTE : Tool J-24095 will hold 1/2 of an ounce of
oil in the tool itself. So if 1 oz . has to be added,
the level of the oil in the bottle should decrease
1-1/2 ounces to add 1 oz . to the system .
CAUTION: When removing the gauge lines
from the fittings, be sure to remove the
adapters from the system fittings rather
than the gauge lines from the adapter.
b. Turn on vacuum pump, and open vacuum
control valve (slowly open high pressure side of
manifold gauge set to avoid forcing oil out of refrig-
erant system and pump).
NOTE : When valve on Tool J-24095 is opened,
the vacuum applied to the discharge side of the
system will suck oil into system from container.
Therefore, close observation of oil level in the
container is necessary.
c. Note level of oil in container. Open valve
on oil adding tool until oil level in container is re-
duced by an amount equal to that lost during dis
charge of system plus 1/2 ounce, then close valve .
Take care not to add more oil than was lost .
d. Disconnect and cap Tool J-24095 and rein-
stall charging station low pressure line to the system .
Open low pressure valve.
EVACUATION
After oil has been added to the system (as ou-
tlined above), run pump until 28-29 inches vacuum
is obtained (See Note under "Evacuating and Charg
ing the System") . Continue to run pump for 10 mi-
nutes after the system reaches 28-29 inches vacuum.
NOTE : If 28-29 inches cannot be obtained, close
Vacuum Control Valve and shut off vacuum
pump . Open Refrigerant Control Valve and al-
low 1/2 pound of R-12 to enter system . Locate
and repair all leaks. Purge this 1/2 pound and
re-evacuate for 10 minutes.
1 . During the ten minute evacuation period, pre-
pare for charging the system by filling the charging
cylinder as follows:
a. Open valve on bottom of charging cylinder
allowing refrigerant to enter cylinder.