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4230 (U5): Heat sink temperature trouble
Abnormal points and detection methods
TH8 detects a temperature outside the specified range
during compressor operation.
TH8: Thermistor <Heat sink>
Diagnosis of failure
Is error code 5110 displayed when
restarted?
Does the fan rotate during com-
pressor operation?
Is there any obstacle which blocks
an airflow around the heat sink?
Check the wiring and connector connection of TH8.
Is there any abnormality such as
disconnection, looseness or break-
age?
Check the resistance of TH8.
Is the resistance normal?
OCH800A_56
Yes
No
No
Yes
Yes
(air path blocked)
No
(no obstacle)
Yes
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 error code 5110.
Refer to the diagnosis of error code 4400.
Improve the airflow path.
Connect the wiring/connector properly.
Replace it in the case of breakage.
TH8 temp. - resistance characteristic
32°F (0°C)
180 kΩ
77°F (25°C)
50 kΩ
122°F (50°C)
17 kΩ
158°F (70°C)
8 kΩ
194°F (90°C)
4 kΩ
Replace the thermistor
(Defective thermistor).
Replace the outdoor power circuit board
(Defective outdoor power circuit board).
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