Code 231-8AF0: Encoder %1 defective
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Encoder %1 defective 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] - Scale or scale tape contaminated or defective - Scanning head contaminated or defective - Signal cable defective - Encoder input defective on the control - Penetration of humidity - The position encoder is contaminated - Motor encoder cable defective - Motor control board defective [Error correction] - Inform your service agency - Exchange the position encoder - Check the encoder cable - Exchange the motor control board (or better, the control) 10/2023 [425]
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 231-8AF0 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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