Hitachi RAS-H(V)RNME-AF Service Manual page 373

12 Troubleshooting
22
Abnormal operation of the thermistor for the outdoor temperature (outdoor unit ambient
Alarm code
thermistor)
• 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
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
Phenomenon
Faulty ther-
mistor for the
outdoor unit
ambient
Faulty PCB1
363
SMGB0070 rev. 1 - 08/2011
No
Connect it
No
Faulty thermistor
Ambient Temperature (ºC)
Cause
Fault
Incorrect connection
Outdoor temperature thermistor
Check item
Check resistance
Check wiring to PCB1 Repair wiring and connections
Replace PCB1 and
check operation
Outdoor unit
ambient
thermistor
Action
(Turn OFF the main switch)
Replace thermistor if faulty
Replace PCB if faulty
12