Hitachi RAS-2-HVNP Service Manual page 203

8. Troubleshooting
Phenomenon
Excessively high dis-
charge pressure
Insufficient cooling
process
Malfunction or internal leakage of the 4-way valve
Excessively low suction
pressure
Discharge temp. of the indoor unit is unstable
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SMGB0079 rev.0 - 01/2013
Cause
Clogging of the outdoor unit
Obstacles at the inlet or the
Insufficient air flow to
outlet of the outdoor unit heat
the outdoor unit heat
exchanger
Is the service area for the out-
Short-circuited air to the out-
Excessively high air
temp. to the outdoor
Any other heat load near the
unit heat exchanger
Excessively charged
Expansion valve opening
refrigerant
Non-condensate gas Check each temp. and each
in cycle
Clogging of the dis-
charge piping
Check the connection cord and
Is there an operation sound
Failure or malfunction
of the expansion valve
Is the thermistor on the com-
Is the thermistor installed cor-
rectly on the compressor?
Check the temp. difference at
the inlet and the outlet of the
Malfunction or internal Check the Temp. Difference be-
leakage of the 4-way tween the Inlet and the Outlet
valve
Failure of solenoid Check refrigerant leakage of
valve for bypass
Check the expansion valve
of the indoor unit in the same
Check item
(Turn OFF the main switch)
Remove the clogging
heat exchanger?
Remove the obstacles
exchanger
Secure the service area
door unit sufficient?
Correct fan speed? Replace the fan motor
Remove the cause of the short-
door unit?
Remove the heat source
outdoor unit?
Correctly charge the refrigerant
Charge the refrigerant after the
pressure
Check for clogging Remove the clogging
Check for clogging Remove the clogging
Replace the connector
the connector
from the coil?
Replace the thermistor
pressor normal?
Correctly install the thermistor
Replace the 4-way valve
4-way valve
Replace the 4-way valve
of 4-Way Valve
Replace solenoid valve
solenoid valve
Replace the failed expansion
valve of the indoor unit
system
Action
circuited air
vacuum pumping
Replace the coil
8