Hitachi Utopia RPI-2.5HRG Service Manual page 47

TROUBLESHOOTING
Alarm
Code
G "RUN" light flickers and "ALARM" is indicated on the remote control switch.
G The unit No., alarm code and the unit code is alternately indicated on the set temperature section,
and the alarm code is indicated on the display of the outdoor unit PCB.
# In the case that the evaporating temperature (Cooling: Liquid Refrigerant Piping Temp. of Indoor
Unit, Heating: Evaporating Temp. of Outdoor Unit) is lower than -35 deg. 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.
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.
Phenomenon
Faulty Freeze
Protection
Thermistor of
Indoor Unit
Evaporating
Thermistor of
Outdoor Unit
(Outdoor Unit, Indoor Unit)
Excessively
Low Suction
Pressure
(in Vacuum)
1-44
Activation to Protect System from Excessively Low Suction Pressure
No
Yes
No
Yes
No
Yes
Cause
Fault
Incorrect Connection
Faulty PCB
Liquid Line Stop Valve
is not in Operation
Faulty or Malfunction of
Expansion Valve
Refrigerant Leakage
(Protection from Vacuum Operation)
Connect it.
Connect it.
Faulty thermistor.
Is gas leaking?
Yes
Repair leaks of gas.
Check Item
Check resistance.
Check wiring to PCB.
Replace PCB and
check operation.
Check stop valve.
Check for clogging.
Check connecting
wiring and connectors.
Check operating sound
from coil.
Check discharge gas
thermistor.
Check attaching
state of discharge
gas thermistor.
Check each temp.
and pressure.
Check gas leakage part.
No
Recharge refrigerant.
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.