Troubleshooting
SiBE041012_B
78
Service Diagnosis
4.8
Low-voltage Detection or Over-voltage Detection
Error Code
U2
Method of Error
Detection
Indoor Unit
The zero-cross detection of the power supply is evaluated 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 150 ~ 180 V (depending on
the model).
The compressor stops if the error occurs, and restarts automatically after 3-minute standby.
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.
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 indoor unit PCB
