Hitachi RASC-4HNPE Service Manual page 231

10 Troubleshooting
Troubleshooting procedure
14
Alarm code
This alarm code is displayed when the thermistor is short-circuited (less than 0.24 kΩ) or cut (greater than 840 kΩ) during
the cooling process or the heating process. The system is automatically restarted when the fault is removed.
Is THM5 (gas pipe) connected to
between 0.24kΩ and 840kΩ?
Phenomenon
Faulty gas piping thermistor
Faulty PCB

Examples of position of the indoor unit heat exchanger gas pipe thermistor (THM5)
THM5
221 SMGB0091 rev.2 - 11/2015
Abnormal operation of the thermistor for the indoor unit heat exchanger gas pipe
temperature (gas piping thermistor)
I.U. PCB?
Yes
Is the resistance of THM5
Yes
Faulty PCB
Cause
Fault
Incorrect connection
Thermistor characteristics
Thermistor
resistance
(kΩ)
No
Connect it
No
Faulty thermistor
Check item
Check the resistance
Check the connection
Replace PCB and check the
operation
Air temperature (ºC)
THM5
Action
(Turn OFF the main switch)
Replace the thermistor if faulty
Repair the wiring and
connections
Replace PCB if faulty
THM5
10