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TM5-4120-387-14
Take care that only a very small amount of refrigerant is
allowed to escape during hose purging.
e.
Loosen hose connections at gages or charging manifold.
f.
Open high (discharge) high pressure charging 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 low (suction) pressure charging valve slightly to purge air from hose.
Tighten low pressure hose connection at gage fitting as soon as a hissing sound is
heard.
h.
Open the low (suction) and high (discharge) charging valves.
i.
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.
j .
Turn the mode selector switch to the COOL mode with the Temperature control
thermostat in the full DECREASE setting for a few minutes.
k.
With the unit operating, allow gages to stabilize. Take readings of the two
gages.
(1) Discharge pressure too high.
Possible causes:
o Dirty or partially blocked condenser coil.
(See para 4-62.)
o Partially blocked condenser fan discharge. (See para 4-20.)
o Loose or missing lower panel (see para 4-24), connector cover plate
(see para 4-16), or circuit breaker access plate (see para 4-17).
o Excessive recirculation of hot condenser discharge air back into
condenser intake.
o Overcharge of refrigerant.
(See para 5-7.)
o Air in refrigerant system.
(See para 2-3.)
o High suction pressure - See (4) below.
o Fan motor not operating.
(See para 4-60.)
5-22
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