Mitsubishi Electric PUMY-P36NKMU2-BS Technical & Service Manual page 77

Check code
Ambient temperature thermistor (TH7) open/short
5106
(U4)
Abnormal points and detection methods
If TH7 detects to be open/short
Open: −40°F [−40:] or less
Short: 194°F [90:] or more
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting
any connectors, or replacing boards.
Check the wiring and connector connection of TH7.
Is there any abnormality such
as disconnection, looseness or
breakage?
Disconnect the connector to check the
resistance of TH7 using a tester.
Is the detected resistance normal?
Check the temperature of TH7.
Is the detected temperature normal?
OCH695B
TH7: Thermistor <Ambient>
Diagnosis
No
Yes
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.
Yes
Replace it in case of breakage.
No
The detected temperature of thermistor (TH7)
The detected temperature of TH7 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 controller board
No
(Malfunction of thermistor circuit).
No abnormality
(A connector contact failure is suspected).
77
Remedy
Replace the thermistor.
Unit
°F