Hitachi UTOPIA RAS-4HVRP2E Service Manual page 217

10 Troubleshooting
Initial troubleshooting
Phenomenon
Excessively high
discharge pressure
Insufficient cooling
process
Malfunction or internal leakage of the 4-way
Excessively low
suction pressure
Discharge temperature of the indoor unit is
215 SMGB0136 rev.0 - 07/2021
Cause
Clogging of the outdoor unit
Obstacles at the inlet or the
Insufficient air flow at
outlet of the outdoor unit heat
the outdoor unit heat
exchanger
Is the service area for the
Excessively high air
temperature to the
outdoor unit heat
Any other heat load near the
exchanger
Excessively charged
Expansion valve opening
refrigerant
Non-condensated gas Check each temperature and
in cycle
Clogging of the
discharge piping
Check the connection cord
Is there an operation sound
Failure or malfunction
of the expansion valve
Is the thermistor installed
correctly on the compressor?
difference at the inlet and the
valve
Malfunction or internal
leakage of the 4-way difference between the inlet
valve and the outlet of 4-way valve
Failure of solenoid Check refrigerant leakage of
valve for bypass
Check the expansion valve
of the indoor unit in the same
unstable
Check item
(Turn OFF the main switch)
heat exchanger?
exchanger
outdoor unit sufficient?
Correct fan speed?
Short-circuited air to the
outdoor unit?
outdoor unit?
Charge the refrigerant after
each pressure
Check for clogging
Check for clogging
and the connector
from the coil?
Is the thermistor on the
compressor normal?
Check the temperature
outlet of the 4-way valve
Check the temperature
solenoid valve
Replace the failed expansion
system
Action
Remove the clogging
Remove the obstacles
Secure the service area
Replace the fan motor
Remove the cause of the
short-circuited air
Remove the heat source
Correctly charge the
refrigerant
the vacuum pumping
Remove the clogging
Remove the clogging
Replace the connector
Replace the coil
Replace the thermistor
Correctly install the
thermistor
Replace the 4-way valve
Replace the 4-way valve
Replace solenoid valve
valve of the indoor unit
10