Ambient Temperature Thermistor (Th7) Open/Short; 5106 - Mitsubishi Electric PUMY-P250YBM Technical & Service Manual

Check code

Ambient temperature thermistor (TH7) open/short

5106

(U4)
Abnormal points and detection methods
If TH7 detects to be open/short.
Open: −40°C or less
Short: 90°C or more TH7: Thermistor <Ambient>
●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 multimeter.
Is the detected resistance normal?
Check the temperature of TH7.
Is the detected temperature normal?
OCH760
Diagnosis
No
Yes
Yes
Causes and checkpoints
Disconnection or contact failure of connectors
Characteristic defect of thermistor
Defective outdoor multi controller circuit board
The black square (■) indicates a switch position.
Connect the wiring/connector properly.
Yes
Replace it in the case of breakage.
No
The detected temperature of thermistor (TH7)
The detected temperature of TH7 can be displayed by an
can be displayed by an operation of SW1 on the
operation of SW1 on the outdoor multi controller circuit board.
outdoor multi controller circuit board.
SW1 Setting Display on LED1, 2
ON
−99.9–999.9
OFF
1 2 3 4 5 6 7 8
Replace the outdoor multi controller circuit
No
board (Malfunction of thermistor circuit).
No abnormality
( A connector contact failure is suspected.)
68
Remedy
Replace the thermistor.
Unit
°C