Hitachi UTOPIA RAS-4HVRP2E - Page 250

10 Troubleshooting
Troubleshooting procedure
SMGB0136 rev.0 - 07/2021
248
Alarm code
22
Abnormal operation of the thermistor for the outdoor temperature
(outdoor unit ambient thermistor) (THM7)
• 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.
• This alarm forces all operations to stop (Outdoor & Indoor Units).
• The unit should be stopped to release the alarm.
Is the thermistor THM7
(TA) connected to PCB1?
Connect it
No
Yes
Is the resistance of
THM7between0.24kΩ
and500kΩ?
Faulty thermistor
No
Yes
Faulty PCB1
Outdoor unit ambient thermistor
(THM7)
105,4
77,9
58,2
44,0
33,6
25,9
20,2
15,8
12,5
10,0
8,0
6,5
5,3
4,3
3,6
3,0
2,5
0
20
40
60
80
100
120
-20-15 -10-50 51015202530354045505560
Thermistor resistance characteristics
Temperature (ºC)
Thermistorresistance(kΩ)
Phenomenon Cause Check item
Action
(Turn OFF the main switch)
Faulty thermistor for the
outdoor unit ambient
Fault Check resistance Replace thermistor if faulty
Incorrect connection Check wiring to PCB Repair wiring and connections
Faulty PCB
Replace PCB and check
operation
Replace PCB if faulty