Hitachi UTOPIA RAS-4HVRP2E - Page 273

10 Troubleshooting
Troubleshooting procedure
SMGB0136 rev.0 - 07/2021
271
10
Alarm code
12
Abnormality of Thermistor for Indoor Unit Outlet Air Temperatures (Outlet Air Thermistor)
• Thealarmcodeisashedonthe7-segmentdisplayoftheoutdoorunit.
• The alarm code is displayed on the wired controller of the indoor unit.
Thisalarmcodeisdisplayedwhenashortcircuit(0.24kΩorless)ordisconnection(840kΩormore)ofthethermistoris
detected during a heating or cooling operation. The operation automatically restarts when the malfunction is removed.
Phenomenon Cause
Check Item
Action (Turn OFF
Main Switch)
Failure of Outlet Air
Thermistor
Failure of Indoor Unit PCB
Failure
Incorrect Connection
Check resistance
Check wiring
to Indoor Unit PCB
Replace Indoor Unit PCB and
check operation
Replace thermistor if faulty
Correctly connect wires
Replace Indoor Unit PCB if
faulty
Failure of Thermistor
Failure of Indoor Unit PCB
Is resistance of THM2
between0.24kΩand840kΩ?
Is thermistor THM2 (for outlet
air temp.) connected to THM2
of indoor Unit PCB?
Yes
Yes
No
No
Connect them
Refer to “Alarm Code 11”
for thermistor resistance