Fagor alarm 4121: ERROR 109: Over-voltage at digital inputs
CNC 8055 SERCOS drive error (DDS) · Fagor DDS drives
What it means
A voltage above the configured level has been applied to the drive's digital inputs. This error cannot be reset by command; correct the wiring/voltage and power-cycle the servo system. The CNC stops all motion and activates the external emergency output.
Likely causes
- 24 V applied to inputs configured for another level (IP5 mismatch)
- Wiring error or voltage surge on the PLC I/O lines
- Faulty external device feeding an input
Need the part urgently?
Send us alarm 4121 with your machine details — typical RFQ turnaround is 24–48h.