Heat Sink Temperature Trouble - Mitsubishi Electric PUMY-P250YBM Technical & Service Manual

Check code
4230
(U5)
Abnormal points and detection methods
If TH8 detects a temperature outside the specified range during
compressor operation.
TH8: Thermistor <Heat sink>
●Diagnosis of defects
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Is 5110 displayed when restarted?
Does the fan rotate during
compressor operation?
Is there any obstacle which
blocks an airflow around the heat
sink?
Check the wiring and connector connection TH8.
Is 5110 displayed when restart?
Is there any abnormality such
as disconnection, looseness or
breakage?
Check the resistance of TH8.
Is the resistance normal?
OCH760

Heat sink temperature trouble

Diagnosis
No
Yes
(air path blocked)
(no obstacle)
No
No
Yes
Causes and checkpoints
Blocked outdoor fan
Malfunction of outdoor fan motor
Blocked airflow path
Rise of ambient temperature
Characteristic defect of thermistor
Malfunction of input circuit on outdoor power circuit board
Malfunction of outdoor fan driving circuit
Refer to the diagnosis of check code 5110.
Yes
Refer to the diagnosis of check code 4400.
No
Yes
Connect the wiring/connector properly.
Yes
Replace it in the case of breakage.
TH8 temp. - resistance characteristic
0 ···180 kΩ 25 ···50 kΩ 50 ···17 kΩ
70 ···8 kΩ 90 ···4 kΩ
Replace the thermistor
No
(Defective thermistor).
Replace the outdoor power circuit board
(Defective outdoor power circuit board).
62
Remedy
Improve the airflow path.