Hitachi UTOPIA RAS-4HVRP2E Service Manual page 254

10 Troubleshooting
Troubleshooting procedure
47
Alarm code
• In the case that the evaporating temperature (Cooling: Liquid Refrigerant Piping Temperature of Indoor Unit,
Heating: Evaporating Temperature of Outdoor Unit) is lower than -37 ºC (250~350 kΩ) and the thermistor on top of
compressor is higher than 90 ºC for 10 minutes, retry operation is performed 3 minutes after compressor stoppage.
However, when the state occurs more than 3 times including 3 in one hour, this alarm code is indicated.
• This alarm forces all operations to stop (Outdoor & Indoor Units).
• The unit should be stopped to release the alarm.
Is the thermistor THM8 of
outdoor unit connected to PCB1?
Is the thermistor THM3 of indoor
unit connected to PCB?
Is resistance of THM3 and THM8
between 0.24kΩ and 500kΩ?
Is gas leaking?
Repair leaks of gas
Phenomenon
– Faulty indoor unit liquid
refrigerant temperature
thermistor
– Faulty outdoor unit
evaporating temperature
thermistor
Faulty PCB (Outdoor Unit, Indoor Unit)
Excessively low suction
pressure (in vacuum)
Faulty outdoor fan at heating
operation
252 SMGB0136 rev.0 - 07/2021
Activation to Protect System from Excessively Low Suction Pressure
(Protection from Vacuum Operation)
No
Yes
No
Yes
No
Yes
No
Yes
Cause
Fault
Incorrect Connection
Liquid line stop valve is not
open before operation
Faulty or malfunction of
Check operating sound from coil.
expansion Valve
Refrigerant Leakage
Faulty outdoor fan motor
Connect it
Connect it
Faulty thermistor
Recharge refrigerant
Check item
Check resistance.
Check wiring to PCB.
Replace PCB and check the
operation.
Check stop valve.
Check for clogging.
Check connecting wiring and
connectors.
Check discharge gas thermistor.
Check attaching state of
discharge gas thermistor.
Check each temperature and
pressure.
Check gas leakage part.
Measure coil resistance and
insulating resistance.
Action
(Turn OFF Main Switch)
Replace thermistor if faulty.
Repair wiring and connections.
Replace PCB if faulty.
Fully open stop valve.
Remove clogging.
Replace connector.
Replace coil.
Replace thermistor.
Reattach thermistor.
Charge refrigerant after
vacuum pumping.
Correctly charge refrigerant after
repairing gas leakage.
Replace outdoor fan motor if
faulty.