Code 320-07D4: Supply voltage missing at X44
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Supply voltage missing at X44 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
[Cause of error] No supply voltage is applied at connector X44 of the control (= Relay external DC voltage missing). Possible causes: - PLC fuses defective - 24V power supply unit in the electrical cabinet defective - Faulting wiring of 24 V supply - Lines interrupted [Error correction] - Check the PLC fuses - Check the 24 V power supply unit in the electrical cabinet - Check the wiring of the 24 V supply - Check the lines for interruption
Source: HEIDENHAIN NC Error Messages — TNC7/640/620/320/128, CNC PILOT 640, MANUALplus 620 (10/2023)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Heidenhain TNC Series CNC Alarms
Heidenhain controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 320-07D4 on the TNC Series CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Heidenhain's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4497 Heidenhain TNC Series CNC codes.
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