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TM5-4120-377-14
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 service valve slightly to purge air from hose. Tighten high pressure
hose connection at gage-fitting as soon as a hissing sound is-heard.
g. Open low (suction) pressure service valve slightly to purge air
connection at gage fitting as soon as a hissing sound is heard.
h. Open the low (suction) and high (discharge) service valves.
i.
Both gages should read the same. Check the reading with the
from hose. Tighten low pressure hose
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:
l
l
l
l
l
l
l
Dirty or partially blocked condenser coil.
Partially blocked condenser fan discharge.
Loose or missing lower front panel, connector cover plate, circuit breaker access cover, or filter
mounting plate.
Excessive recirculation of hot condenser discharge air back into condenser intake.
Overcharge of refrigerant.
Air in refrigerant system.
High suction pressure - See (4) below.
Fan motor not operating.
Condenser fan loose on shaft.
Too much oil in refrigerant system.
(2) Discharge pressure too low.
Possible causes:
Cold outside air.
Low refrigerant charge.
Compressor not operating.
5-19
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