SiBE121123_A Troubleshooting for Outdoor Unit
Service Diagnosis 180
7.2 Low-voltage Detection or Over-voltage Detection
Error Code
U2
Method of Error
Detection
Indoor Unit
Evaluation of zero-cross detection of power supply by the indoor unit PCB.
Outdoor Unit
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
Indoor Unit
There is no zero-cross detection in approximately 10 seconds.
Outdoor Unit
Low-voltage detection:
The voltage detected by the DC voltage detection circuit is below 180 V.
Over-voltage detection:
An over-voltage signal is fed from the over-voltage detection circuit to the microcomputer.
The compressor stops if the error occurs, and restarts automatically after 3-minute standby.
If the error repeats, the system is shut down.
Reset condition: Continuous run for about 60 minutes without any other error
Supposed
Causes
Power supply voltage is not as specified.
Defective DC voltage detection circuit
Defective over-voltage detection circuit
Defective PAM control part
Disconnection of compressor harness
Short circuit inside the fan motor winding
Noise
Momentary fall of voltage
Momentary power failure
Defective outdoor unit PCB
Defective indoor unit PCB
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