Hitachi FSG Series Service Manual page 43

Alarm Code
12
n "RUN" light flickers and "ALARM" is indicated on the remote control switch.
n The unit No., alarm code and the unit code is alternately indicated on the set temperature section, and the
unit No. and alarm code are indicated on the display of the outdoor unit PCB.
‘
This alarm code is indicated when the thermistor is short-circuited (less than 0.24 kW) or cut (greater than
840 kW) during the cooling or heating operation. The system is automatically restarted when the fault is
removed.
Is it connected to THM2
(intake) of PCB.
Yes
Is resistance of THM2
between 0.24kW and 840kW?
Yes
Faulty PCB
Phenomenon
Faulty Intake
Air Thermistor
Faulty PCB
Abnormality of Thermistor for Indoor Discharge Air Temperature
(Air Outlet Thermistor)
No
Connect it.
No
Faulty Thermistor
Refer to page 1-34 for
thermistor resistance
.
Cause
Fault
Incorrect Connection
TROUBLESHOOTING
Indoor Unit
Air outlet Thermistor
(THM2)
Check Item
Check resistance.
Check connection.
Replace PCB and Check
operation
1
35
In case of 4-Way
Cassette
Action
(Turn OFF main switch)
Replace thermistor if
faulty.
Repair wiring and
connections.
Replace PCB if faulty