Siemens alarm 2120: NCK fan alarm type %1
SINUMERIK NCK general alarm · Siemens 840D/810D powerline
What it means
Fan speed monitoring at the NC module has responded for the fan identified by parameter %1. One of the fans in the NCU/NCU box is stalled, running below its nominal speed, or its tach signal is not being read. Cooling capacity is reduced and the NCK may overheat and shut down or raise alarm 2110 if the fan is not restored.
Likely causes
- Fan bearing worn out or fan jammed by dust/debris
- Fan cable or tach signal line loose or broken
- Fan end-of-life (typical service life 3-6 years in continuous duty)
- Incorrect fan type configured for the monitored position
Triage note: Parameter %1 identifies which fan slot responded; match replacement fan to NCU variant (classic NCU box vs NCU 7xx sl).
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
- Request a quote →
6FC5247-0AA30-0AA0
fan · Common cause
Need the part urgently?
Send us alarm 2120 with your machine details — typical RFQ turnaround is 24–48h.