Hitachi RAS-2-HVNP Service Manual page 237

8. Troubleshooting
24
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. (*1)
If you find an abnormal operation of the thermistor, check all the thermistors as shown below.
- The evaporating thermistor during the heating process is attached to the heat exchanger as shown in the figure
below. If this the thermistor is faulty, such as short-circuit (less than 0,2kΩ) or cut (more than 500kΩ) during opera-
tion, this alarm is displayed. The position is indicated below.
Phenomenon
Faulty thermistor for the
evaporating temperature during
heating
Faulty PCB
Thermistor
Resistance
(kΩ)
223
SMGB0079 rev.0 - 01/2013
Abnormal operation of the thermistor for the evaporating temperature during the heating process
Cause
Fault
Incorrect Connection
90
80
74
70
60
56
50
43
40
33
30
26
20
20
10
0
-15 -10 -5 0 5 10 15
Ambient Temperature (
Ambient and Evaporating Temp. Thermistor Characteristics
for Outdoor Unit
(outdoor unit)
Check item
Check the resistance
Check the wiring to PCB
Replace PCB and
check the operation
16 12.5
10
8
5.3
3.6
20 25 30 35 40 45 50
C)
o
Action
(Turn OFF the main switch)
Replace the thermistor if faulty
Repair the wiring and the
connections
Replace PCB if faulty
2.5
55 60
8