Service Manual
Table Of Contents
- Cover
- Table of contents
- Part 1 List of Functions
- Part 2 Specifications
- Part 3 Printed Circuit Board Connector Wiring Diagram
- Part 4 Refrigerant Circuit
- Part 5 Functions and Control
- Part 6 Test Operation and Field Settings
- Part 7 Remote Controller
- Part 8 Troubleshooting
- 1. Troubleshooting with LED
- 2. Service Diagnosis
- 3. Error Codes and Description
- 4. Troubleshooting for CTXG, CTXS, FTXS, CDXS, FDXS, FVXS Series
- 5. Troubleshooting for FFQ Series
- 6. Troubleshooting for Branch Provider (BP) Unit
- 7. Troubleshooting for Outdoor Unit
- 8. Thermistor Resistance/Temperature Characteristics
- 9. Pressure Sensor
- 10. Method of Replacing Inverter’s Power Transistors Modules
- Part 9 Appendix
Troubleshooting for Branch Provider (BP) Unit SiUS181631EA
222 Troubleshooting
6.4 Signal transmission Error between Indoor Unit and
Branch Provider (BP) Unit
Error Code
U4
Method of Error
Detection
The signal transmission data from the BP unit is checked whether it is normal.
Error Decision
Conditions
When the data sent from the BP unit cannot be received normally, or when the content of the data
is abnormal.
Supposed
Causes
Defective BP unit PCB
Defective indoor unit PCB
Signal transmission error due to wiring error
Signal transmission error due to disturbed power supply waveform
Signal transmission error due to breaking of connection wires (wire No. 2)