Hitachi Utopia RPI-2.5HRG Service Manual page 33

TROUBLESHOOTING
Alarm
Code
G "RUN" light flickers and "ALARM" is indicated on the remote control switch.
G The unit No., alarm code and the unit code is alternately indicated on the set temperature section,
and the alarm code is indicated on the display of the outdoor unit PCB.
# This alarm code is indicated when the thermistor is short-circuited (less than 0.24 kΩ) or cut (greater
than 840 kΩ) during the cooling or heating operation. The system is automatically restarted when the
fault is removed.
Is it connected to
THM1 (intake) of PCB?
Yes
Is resistance of THM1
between 0.24kΩ and
840kΩ?
Yes
Faulty PCB
Phenomenon
Faulty Intake
Air Thermistor
Thermistor
Resistance
(KΩ)
NOTE:
This data is applicable to the following thermistors;
1. Indoor Unit Discharge Air Temperature, 2. Indoor Unit Liquid Refrigerant Temperature, 3 Indoor Unit
Intake Air Temperature, 4. Outdoor Air Temperature, 5. Outdoor Unit Evaporating Temperature, 6. Indoor
Unit Gas Piping
1-30
Abnormality of Thermistor for Indoor Unit Inlet Air Temperature
No
Connect it.
No
Faulty Thermistor
Cause
Fault
Incorrect Connection
Faulty PCB
90
82
80
70
61
60
50
46
40
35
30
27
20
10
0
-15 -10 -5 0 5 10
Ambient Temperature (
Thermistor Characteristics
(Air Inlet Thermistor)
In Case of 4-Way Cassette Type
Check Item
Check resistance.
Check connection.
Replace PCB and
check operation.
20.5
16
12.5
10
8
5.3
15 20 25 30 35 40
o
C)
Indoor Unit
Air Inlet Thermistor
Action
(Turn OFF Main Switch)
Replace thermistor
if faulty.
Repair wiring and
connections.
Replace PCB if faulty.
3.6
2.5
45 50 55 60