GMC 4000 Series Service Manual page 92

b. Connect flexible line from center fitting of
the gauge set to refrigerant container (container
should be at room temperature).
NOTE: It may be necessary to use reducer
fitting J-8695-18 if attaching flexible hose to drum-
type refrigerant container.
c. Open shut-off valve on container and loosen
flexible line fitting at center fitting at gauge set so
that refrigerant will purge all air from line. Tighten
flexible fitting when certain all air has been purged
from line.
d. Open suction valve on gauge set. This will
allow refrigerant to pass from the container into
the system . When pressure stops rising, close suc­
tion valve on gauge set and valve at refrigerant
container (as refrigerant container is at room
temperature, only a small refrigerant charge will
enter the system ).
e. Using leak detector J-6084, check all fit­
tings in the system , com pressor shaft seal and on
the gauge set for evidence of leakage. When general
area of leak has been found with the test torch, a
liquid leak detector may be helpful in locating the
exact point of leakage. After leak has been cor­
rected, evacuate the system again for 15 to 20
minutes.
6. Turn the hand shut-off valves at the low
and high pressure gauge of the gauge set to the full
clockwise position with the vacuum pump operating,
then stop pump. Carefully check low pressure gauge
to see that vacuum remains constant. If vacuum
reduces, it indicates a leak in the system or gauge
connections. See "NOTE" in step 5 previously for
method of locating leak.
CHARGING THE SYSTEM
The system should be charged only after being
evacuated as outlined in "Evacuating The System ."
REFRIGERANT DRUM METHOD
1. Connect center flexible line of gauge set to
refrigerant drum.
NOTE: It may be necessary to use adapter
J-8695-18 to attach flexible line to refrigerant
drum.
2. Place refrigerant drum in a pail of water
which has been heated to a maximum of 125°F.
CAUTION: Do not allow temper­
ature of water to exceed 125°F. High
temperature will cause excessive p res­
sure and possible softening of the fus­
ible safety plugs in the refrigerant
drum. It may not be necessary to use
hot water if a large drum is used (over
approximately 100 pounds).
G M C S E R V I C E M A N U A L
sca les (bathroom or commercial, preferably com ­
mercial) (fig. 12).
purged of air, loosen line at center fitting on gauge
set and "crack" valve on refrigerant drum to blow
air from line. Retighten line at center fitting and
record exact weight of refrigerant tank in water
on the scales.
valves on gauge set to allow refrigerant to flow
into the system . Continue charging until the scales
show that 3 -1/4 pounds of refrigerant have been
transferred from refrigerant drum to the system .
both valves on gauge set, start engine, place "AIR
COND" lever to "ON," the "AIR" lever to "OUT-
SIDE," and then place "TEMP" lever to full cold
position. Open low pressure valve on gauge set
slowly and leave open until full charge of 3-1/4
pounds of Refrigerant-12 is taken in.
sure valve will already be closed if charging was
completed by running compressor) and close valve
on refrigerant drum.
Refrigerant-12 charge into the system, close valve
on refrigerant drum to permit compressor to draw
any refrigerant left in the line from the drum to
the center fitting of the gauge set, then close the
low pressure valve on the gauge set.
control knob at full cold position and blower con­
trol for high speed with "AIR" lever to "OUTSIDE."
After ten minutes of operation observe appearance
of refrigerant in receiver-dehydrator. If bubbles
are observed, open low pressure gauge valve and
valve on refrigerant drum to allow more refriger­
ant to enter system . Close valve when receiver-
dehydrator clears up.
when this check is made, bubbles may appear even
AIR CONDITIONING
3. Place refrigerant drum (in pail of water) on
4. If line at center gauge fitting has not been
CAUTION: When purging a line by
cracking a fitting, wrap a cloth around
connection to prevent injury due to release
of pressurized refrigerant. Also, be sure
to wear eye protection.
5. Open valve on refrigerant drum and both
NOTE: If full charge cannot be attained, close
CAUTION: Observe high pressure
gauge while charging with compressor
running. Shut off engine if pressure ex­
ceeds 375 psi. A large fan placed in
front of the vehicle will help reduce
excessively high head pressure.______
6. Close both valves on gauge set (high p res­
NOTE: If the engine was used to complete the
7. Operate engine at 2000 rpm with "TEMP"
NOTE: If air inlet temperature is below 70°F.,
Sec. 1
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