Hitachi RAS-5HVRNM1E Service Manual page 252

8 Troubleshooting
22
Alarm code
• The RUN LED flickers and "ALARM" is displayed on the remote control switch.
• The unit number, the alarm code and the unit code are alternately displayed on the set temperature section.
The unit number and the alarm code are displayed on the display of the outdoor unit PCB.
– This alarm code is displayed when the thermistor is short-circuited (less than 0.2 kΩ) or cut (greater than 500 kΩ)
during the operation. However, this alarm occurs during the test run mode only. In the case that the thermistor is
abnormal during the operation, the operation continues based on the assumption that the outdoor temperature is
35 °C (cooling) / 6 °C (heating).
Is the thermistor THM7 (TA)
connected to PCB1?
Yes
Is the resistance of THM7
between 0.24 kΩ and 500 kΩ?
Yes
Faulty PCB1
Phenomenon
Faulty thermistor for the outdoor unit
ambient
Faulty PCB1
244
SMGB0060 rev. 1- 12/2010
Abnormal operation of the thermistor for the outdoor temperature (outdoor unit ambient
No
No
Faulty thermistor
Thermistor characteristics
90
80
70
60
50
40
30
20
10
0
-15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60
Ambient temperature (ºC)
Cause
Fault
Incorrect connection
thermistor) for IVX Series
Connect it
Check item
Check resistance
Check wiring to PCB
Replace PCB1 and check operation
Outdoor
unit ambient
thermistor
Action
(Turn OFF Main Switch)
Replace thermistor if faulty
Repair wiring and connections
Replace PCB if faulty