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TM 9-4120-389-14
c. Connect individual pressure gages, or a refrigeration charging manifold and hoses to the high
(discharge) and low (suction) charging valves.
CAUTION
Take care that only a very small amount of refrigerant is allowed to escape during hose purging.
d. Loosen hose connections at gages or charging manifold.
e. Open high (discharge) high pressure manifold valve slightly to purge air from hose. Tighten low
pressure hose connection at gage fitting as soon as a hissing sound is heard.
f. Open low (suction) pressure manifold valve slightly to purge air from hose. Tighten low pressure hose
connection at gage fitting as soon as a hissing sound is heard.
g. Open the low (suction) and high (discharge) manifold valves.
h. Both gages should read the same. Check the reading with the appropriate column in table 5-1. If the
system is even partially charged, the pressure should be approximately equal to that shown in the table for the
appropriate ambient temperature. If the pressure is considerably less than shown in the table, the system does
not contain enough refrigerant to continue the pressure check; go to leak testing.
i. Turn the mode selector switch to the COOL mode with the temperature control thermostat in the full
DECREASE setting for a few minutes.
j. With the unit operating, allow gages-to stabilize. Take readings of the two gages.
k. Refer to Section III Troubleshooting Table to isolate malfunction.
l. When pressure tests are completed, proceed with the maintenance action indicated.
m. Turn unit OFF.
n. Close manifold valves.
5-18
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