Mitsubishi Electric MXZ-SM36NAM2 Technical & Service Manual page 81

Check code
Compressor temperature thermistor (TH4) open/short
5101
(U3)
<Detected in outdoor unit>
Abnormal points and detection methods
If TH4 detects to be open/short.
(The open/short detection is disabled for 10 minutes after compressor
starts, during defrosting operation, or for 10 minutes after returning from
the defrosting operation. The detection is also disabled when the outdoor
temperature is 41°F [5°C] or less in cooling operation, and −4°F [−20°C] or
less in heating.)
Open: 37.4°F [3 ] or less
Short: 422.6°F [217 ] 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 TH4
Is there any abnormality such
as disconnection, looseness or
breakage?
Disconnect the connector to check the
resistance of TH4 using a multimeter.
Is the detected resistance normal?
Check the temperature of TH4.
Is the detected temperature normal?
OCH810A
TH4: Thermistor <Compressor>
Diagnosis
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 the connector in case of breakage.
Replace the thermistor.
The detected temperature of TH4 can be displayed
by an operation of SW1 on the 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
(Malfunction of thermistor circuit).
No abnormality
(A connector contact failure is suspected).
81
Remedy
Unit
°F