5110
(U4)
Heat sink temperature thermistor (TH8) open/short
Abnormal points and detection methods Causes and check points
Abnormal if TH8 detects to be open/short.
Open: −31.2°F [−35.1 ] or less
Short: 338.5°F [170.3 ] or more
TH8: Thermistor <Heat sink>
Disconnection or contact failure of connectors
Characteristic defect of thermistor
Defective outdoor multi controller circuit board
●Diagnosis of defectives
Make sure to turn the power OFF before connecting/disconnecting
any connectors, or replacing boards.
Diagnosis Remedy
outdoor
The black square (■) indicates a switch position.
SW1 Setting
ON
OFF
Display on LED1, 2
Unit
41 2 5 6 7 83
°F
−99.9–999.9
No
Yes
Yes
Yes
No
No
Yes
No
Is there any abnormality such
as a disconnection, looseness or
breakage?
Is the detected resistance normal?
Is the detected temperature normal?
Connect the wiring/connector properly.
Replace it in case of a breakage.
Replace the thermistor.
Replace the outdoor multi controller circuit
board (Malfunction of thermistor circuit).
No abnormality
( A connector contact failure is suspected.)
Check the wiring and connector connection of TH8.
Disconnect the connector to check the
resistance of TH8 using a tester.
Check a temperature of TH8.
The detected temperature of thermistor (TH8)
can be displayed by an operation of SW1 on the
outdoor controller board.
The detected temperature of TH8 can be displayed by
an operation of SW1 on the outdoor controller board.
Is it a model with internal
thermistor?
85
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