Mitsubishi Electric PUMY-P36NKMU2-BS Technical & Service Manual page 79

Check code
Heat sink temperature thermistor(TH8) open/short
5110
(U4)
Abnormal points and detection methods
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>
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting
any connectors, or replacing boards.
Is it a model with internal
Yes
thermistor?
Check the wiring and connector connection of TH8.
Is there any abnormality such
as disconnection, looseness or
breakage?
Disconnect the connector to check the
resistance of TH8 using a tester.
Is the detected resistance normal?
Check the temperature of TH8.
Is the detected temperature normal?
OCH695B
Diagnosis
No
Yes
No
No
Yes
No
Yes
Causes and checkpoints
Disconnection or contact failure of connectors
Characteristic defect of thermistor
Defective outdoor controller board
The black square (■) indicates a switch position.
Connect the wiring/connector properly.
Replace it in case of breakage.
Replace the thermistor.
The detected temperature of thermistor (TH8)
The detected temperature of TH8 can be displayed by
can be displayed by an operation of SW1 on the
an operation of SW1 on the outdoor controller board.
outdoor controller board.
SW1 Setting Display on LED1, 2
ON
−99.9–999.9
OFF
1 2 3 4 5 6 7 8
Replace the outdoor controller board
(Malfunction of thermistor circuit).
No abnormality
(A connector contact failure is suspected.)
79
Remedy
outdoor
Unit
°F