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Troubleshooting
SiMT041311E
171
Service Diagnosis
2.35 Signal Transmission Error (Between Indoor Unit and
Outdoor Unit)
Error Code
U4
Method of Error
Detection
The data sent from the outdoor unit is checked for problem.
Error Decision
Conditions
The data sent from the outdoor unit cannot be received without error, or the disable status of
signal transmission continues for 15 seconds.
Supposed
Causes
Wiring error
Breaking of the connecting wires between the indoor unit and the outdoor unit
Improper insulation of the connecting wires and earth
Wiring length exceeds the specified range
Defective outdoor unit PCB
Defective indoor unit PCB
Layer short inside the fan motor winding