409

Unexpected Disturbance Torque Detected

Fanuc · Alpha i series AC Servo Motor

What does 409 mean?

This alarm indicates that an unexpected disturbance torque has been detected on the servo motor, signaling an abnormal load condition. If the issue is not mechanical, it may stem from an incorrectly set alarm threshold.

Common Causes

  • Abnormal mechanical load acting on the servo motor.
  • Parameter No. 096 (Unexpected disturbance torque detection threshold) is set too low for the application.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Investigate the mechanical system for any abnormal loads, obstructions, or wear.

  2. 2

    Increase the value of parameter No. 096 to a value greater than the observed maximum torque value, observing load torque first (with bit 1 of parameter No. 014 set to 1 and bit 0 set to 0).

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Verified technical data. Last updated: March 2026

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Source: Fanuc Alpha i series AC Servo Motor