Specifications

Troubleshooting SiBE04-624_B
98 Service Diagnosis
2.16 Low-voltage Detection or Over-voltage Detection
Error Code
U2
Method of Error
Detection
Low-voltage detection:
An abnormal voltage drop is detected by the DC voltage detection circuit.
Over-voltage detection:
An abnormal voltage rise is detected by the over-voltage detection circuit.
Error Decision
Conditions
Low-voltage detection:

The voltage detected by the DC voltage detection circuit is below 150 V.
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If the error repeats, the system is shut down.
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Reset condition: Continuous run for about 60 minutes without any other error
Over-voltage detection:
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An over-voltage signal is fed from the over-voltage detection circuit to the microcomputer.
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The compressor stops if the error occurs, and restarts automatically after 3-minute standby.
Supposed
Causes
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Supply voltage is not as specified.
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Defective DC voltage detection circuit
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Defective over-voltage detection circuit
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Defective PAM control part
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Disconnection of compressor harness
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Layer short inside the fan motor winding
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Defective outdoor unit PCB
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Noise
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Momentary fall of voltage
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Momentary power failure