Chevrolet 1980 Light Duty Truck Service Manual page 76

IB -3 0 AIR C O N D ITIO N IN G
Fig. 1 B-23--Discharging and C o lle cting Oil From System
W ith o u t C harging Station J-2 3 5 0 0 -0 1
3. PERFORM THE ENTIRE EVACUATE AND
CHARGE PROCEDURE
ACCUMULATOR LOW-SIDE PRESSURE SERVICE
FITTING.
4. ADDING OIL TO THE C.C.O.T. A/C SYSTEM
should take place AFTER Discharge AND BEFORE
Evacuation procedures by removing the refrigeration
suction hose at the Accumulator outlet pipe connection,
pouring the correct quantity of refrigerant oil into the hose
or pipe and then properly reconnecting hose to pipe (see
Discharging Step No. 2 and C.C.O.T. Refrigeration Oil
Distribution for specific quantity instructions).
5. Following these procedures will prevent accidental
high-side vehicles system pressure being subjected to the
Charging Station in the event an error is made in valve
sequence during compressor operation to pull in the
Refrigerant-12 charge.
DISPOSABLE CAN OR REFRIGERANT DRUM
METHOD
ADDING OIL TO THE C.C.O.T. A/C SYSTEM
should take place after Discharge and before Evacuation
procedure by removing the refrigeration suction hose at the
Accumulator outlet pipe connection, pouring the correct
quantity of refrigerant oil into the hose or pipe and then
properly reconnecting hose to pipe (see Discharging Step
No. 2 and C.C.O.T. Refrigeration Oil Distribution for
specific quantity instructions).
• If the Refrigerant-12 drum is used, place it on a scale
and note the total weight before Charging. Watch the scale
during Charging to determine the amount of R-12 used.
• If disposable 420 ml (14 ounce) R-12 cans are used,
close the tapping valve and then attach can(s) following
instructions included with the tapping valve or tapping
manifold adapter.
THROUGH THE
1. Connect Manifold Gage Set J-5725-04 as shown in
Figure IB-24.
• LOW pressure gage set valve to Accumulator fitting
• Gage set center hose to Refrigerant-12 source
• High pressure gage set valve to vacuum pump
2. To begin evacuation, with Manifold Gage Set and
Vacuum Pump as illustrated in Fig. IB-24 slowly open high
and low-side gage valves and begin vacuum pump operation.
Pump the system for 15 minutes after low-side gage reaches
711.2-736.6 mm (28"-29") vacuum or more.
In all Evacuation procedures, the specification of
711.2-736.6 mm (28"-29") of Mercury vacuum is used. This
specification can only be reached at or near sea level. For
each 304.8 m (1,000 feet) above sea level, specification
should be lowered by one inch of mercury vacuum. At 1524
m (5,000 feet) elevation only 711.2-736.6 mm (23"-24") of
vacuum is required.
If prescribed vacuum cannot be reached, close vacuum
control valve, shut off pump and look for a leak at
connections or pump.
3. When the system is fully Evacuated, close the high-
side gage set valve and turn OFF the vacuum pump.
4. Watch low-side gage to be sure vacuum holds for
5 (FIVE) minutes at gage set and then proceed to Charging.
5. If Vacuum Does Not Hold For 5 Minutes, charge
system with 240 ml (1/2 pound) Refrigerant-12 and leak
check. Discharge system again then repair leak as necessary.
Repeat Evacuation procedure.
TO BEGIN CHARGING OF THE C.C.O.T. A /C
SYSTEM
1. Start engine, run with choke open and fast idle speed
reduced to normal idle, set A/C control lever on OFF.
2. With the Refrigerant-12 drum or 420 ml (14 oz.)
can(s) inverted, open R-12 source valve(s) and allow 480 ml
(one (1) pound) or 1-2 420 ml 14 oz. can(s) of liquid R-12
to flow into system through low-side Service fitting on
Accumulator (see Figure IB-31).
3. As soon as 480 ml (1 lb.) or 1-2 420 ml (14 oz.)
can(s) of liquid R-12 has been added to system, immediately
engage the compressor, by setting the A/C control lever to
NORM and blower speed on HI, to draw in the remainder
of the R-12 charge.
The Charging operation can also be speeded up by
using a large volume fan to pass air over the condenser. If
condenser temperature is maintained below charging
cylinder temperature, Refrigerant-12 will enter system more
rapidly.
4. Shut off R-12 source valve and run engine for 30
seconds to clear lines and gages.
5. With the engine running, remove the charging low-
side hose adapter from the Accumulator Service fitting.
Unscrew rapidly to avoid excess R-12 escape from system.
CAUTIO N: Never remove a gage line from
its adapter when line is connected to A /C
system. Alw ays remove the line adapter
from the service fitting to disconnect a
line. Do not remove charging hose at set
w hile attached to accumulator. This w ill
result in complete discharge of system
due to the depressed schrader valve in
LIG H T T R U C K S ER V IC E M AN UAL