Chevrolet Light Duty Truck 1973 Service Manual page 72

1A-46 HEATER A N D AIR C O N D IT IO N IN G
only 23 to 24 inches of vacuum can normally be
obtained.
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 moisture which
may have entered the system.
The following procedures are based on the use of the
J-8393 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.
3. Measure oil loss collected as a result of purging the
system.
a. Disconnect the Charging Station low pressure
line. Install Tool J-24095 (with valve closed)
onto the system low pressure fitting. Insert pick­
up tube into graduated container of clean
refrigerant oil (fig. 51).
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.
When removing the gauge lines
CAUTIO N:
from the fittings, be sure to remove the adapters
Fig. 50-Collecting Refrigerant Oil During "Purging"
J-8393
CHARGING
STATION
TO HIGH
PRESSURE
FITTING
OIL
COLLECTING
CAN
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
refrigerant 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 reduced
by an amount equal to that lost during discharge
of system plus 1/2 ounce, then close valve.
care not to add more oil than was lost
d. Disconnect and cap Tool J-24095 and reinstall
charging station low pressure line to the system.
Open low pressure valve (1).
Evacuation
After oil has been added to the system (as outlined
above), run pump until 28-29 inches vacuum is obtained
(See General Note under "Evacuating and Charging the
System"). Continue to run pump for 10 minutes after the
system reaches 28-29 inches vacuum.
NOTE: If 28-29 inches cannot be obtained,
close Vacuum Control Valve (3) and shut off
vacuum pump. Open Refrigerant Control
Valve (4) and allow 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, prepare
for charging the system by filling the charging
cylinder as follows:
a. Open valve on bottom of charging cylinder
allowing refrigerant to enter cylinder.
NOTE: It will be necessary to close bleed
valve periodically to allow boiling to subside
to check level in the sight glass of Charging
Station cylinder.
b. Bleed cylinder valve on top (behind control
panel) as required to allow refrigerant to enter.
When refrigerant reaches desired level (see
"System Capacity"), close valve at bottom of
cylinder and be certain bleed valve is closed
securely.
2. Continue to evacuate for rem ainder of 10 minute
period.
3. Turn hand shut-off valves at low and high pressure
gauges of gauge set to full clockwise position with
vacuum pump operating, then stop pump. Carefully
check low pressure gauge for approximately two
minutes to see that vacuum remains constant. If
Take
LIGHT DUTY TRUCK SERVICE MANUAL