SiUS071735EA
Troubleshooting
Service Diagnosis
76
4.12 Signal Transmission Error (Between Indoor Unit and
Outdoor Unit)
Error Code
U4
Method of Error
Detection
The signal transmission data from the outdoor unit is checked whether it is normal.
Error Decision
Conditions
The data sent from the outdoor unit cannot be received normally, or the content of the data is
abnormal.
Supposed
Causes
Power supply voltage out of specification
Reduction of power supply voltage
Wiring error
Breaking of the connecting wires between the indoor and outdoor units (wire No. 3)
Defective outdoor unit PCB
Short circuit inside the fan motor winding
Defective indoor unit PCB
Disturbed power supply waveform
Summary of Contents for FDMQ-R Series
Page 12: ...SiUS071735EA 1 List of Functions Part 1 List of Functions 1 Functions 2...
Page 14: ...SiUS071735EA 3 Specifications Part 2 Specifications 1 Specifications 4...
Page 120: ...Check SiUS071735EA 109 Service Diagnosis 15 18 24 class R25105 1 2 3 4 Multimeter...
Page 122: ...Check SiUS071735EA 111 Service Diagnosis 15 18 24 class R20704 W V U DC_P1 DC_N1...
Page 140: ...Piping Diagrams SiUS071735EA 129 Appendix RX24RMVJU A 3D092249A...