Code 2120: NCK fan alarm type %1
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical NCK fan alarm type %1 alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Definitions: The fan consists of a 26 V DC mo tor with electronic commutator (rated speed: approx. 8700 rpm). The commutator signal is used for speed m onitoring, response speed: < 7500 rpm. In the case of a fan defect, Solutionline modules can be forced to power off in order to prevent them from mechanical destruction (see M anual: chapter Dual fan/battery module). This applies, if the fan alarm is of type one. Reaction: Alarm display. Remedy: Please inform the authorized personnel/service depar tment. The unit with the fan and NCK battery must be replaced. Program Continuation: Clear alarm with the Delete key or NC START.
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 2120 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
Have a better solution?
Help the industrial community by sharing your repair experience for code 2120.
Need a searchable reference for more Siemens SINUMERIK 840D CNC manuals?
We structure equipment manuals into searchable code, title, cause, solution, safety note, and source-reference data. Send a PDF and example searched codes when you need public pages, private search, or structured exports.
Space reserved for Google AdSense / Industrial Affiliate Links
Monetization target for 2026