Code SV0431: Converter: main circuit overload
Issue Description & Safety Warning
The Fanuc Alpha-i Servo Spindle Amplifier has triggered a critical Converter: main circuit overload 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
Amplifier LED display: 3 Also shown as: SV0431 (15i), SV0431 (30i/31i/32i), SV0431 (0i-D) Cause: (1) Meaning A cooling fan for the control circuit has stopped. With the A06B-6140-HXXX or A06B-6150-HXXX (an upgrade version of PS), this alarm is also issued when a unit stirring fan has stopped. (2) Cause and troubleshooting (a) Cooling fan broken Check whether the cooling fan rotates normally. → Replace it. (b) Internal stirring fan broken (only with an upgrade version of PS) → Replace it.
Source: Fanuc αi Servo/Spindle Amplifier Maintenance Manual (B-65285EN/04) — Part II Troubleshooting
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc Alpha-i Servo Spindle Amplifier Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code SV0431 on the Alpha-i Servo Spindle Amplifier identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Fanuc's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 135 Fanuc Alpha-i Servo Spindle Amplifier codes.
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