Code 320-07D9: Temperature too high (CPU%1 := %2°C)
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Temperature too high (CPU%1 := %2°C) 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] Temperature sensor detects an excessively high temperature within the main computer's housing. - Insufficient heat dissipation for the MC main computer - Contaminated filter pads - Defective climate control unit in the electrical cabinet or operating panel (where MC is installed) - Defective fan - Defective temperature sensor - Unfavorable mounting of components [Error correction] - Clean the filter pads - Check the climate control unit and repair it if necessary - Replace the fan - Inform your service agency 10/2023 [1119]
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 320-07D9 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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