If your CNC machine is displaying a Fanuc servo drive alarm, it can bring your entire production to a halt. Understanding what these alarms mean — and how to resolve them quickly — is critical for any CNC technician or machine operator.
In this guide, we cover the most common Fanuc servo drive alarm codes, their causes, and practical steps to fix them.
What is a Fanuc Servo Drive Alarm?
Fanuc servo drive alarms are error codes displayed on the CNC controller when the servo system detects a fault. These alarms can be caused by electrical faults, mechanical issues, encoder failures, or a faulty servo drive/amplifier.
Most Common Fanuc Servo Drive Alarms
Alarm 401 — Servo Ready Signal Off
Cause: The servo amplifier is not ready. This is usually caused by a power supply issue, a faulty servo drive, or an emergency stop condition that has not been cleared.
Fix: Check the servo amplifier power supply. Inspect the DC link voltage. If the amplifier LED shows an error code, refer to the amplifier fault LED table. Replace the servo drive if faulty.
Alarm 404 — Servo Amplifier Overload
Cause: The servo amplifier has overheated or is drawing excessive current. This can be caused by a blocked cooling fan, a faulty motor, or an overloaded axis.
Fix: Check and replace the cooling fan (Fanuc fans: A90L-0001-0508, A90L-0001-0580). Inspect the servo motor windings for shorts. Check mechanical load on the axis.
Alarm 410 — Servo Motor Overspeed
Cause: The servo motor has exceeded its maximum speed limit. Usually caused by a faulty encoder or incorrect parameter settings.
Fix: Check encoder feedback signal. Inspect encoder cable for damage. Replace encoder if faulty (Fanuc encoders: A860-2020-T301, A860-2000-T301).
Alarm 417 — Digital Servo Parameter Error
Cause: Servo parameters stored in the controller are incorrect or corrupted — often after a battery failure or controller board replacement.
Fix: Restore servo parameters from backup. Replace the CNC battery (A98L-0031-0025) to prevent future data loss.
Alarm 436 — Soft Thermal Alarm
Cause: The servo amplifier thermal model has detected excessive heat buildup in the motor or drive.
Fix: Allow the machine to cool down. Check cooling fan operation. Inspect for mechanical binding on the axis.
When to Replace the Servo Drive
If the alarm persists and the servo drive LED indicates an internal fault, the servo drive may need to be replaced or repaired. Common Fanuc servo drives include the αi series (A06B-6114-Hxxx, A06B-6117-Hxxx) and βi series (A06B-6160-Hxxx, A06B-6164-Hxxx).
At JJ Automation, we stock new and tested used Fanuc servo drives, servo motors, and encoders — all 100% tested before dispatch. We also offer servo drive repair services as a cost-effective alternative to replacement.
Contact JJ Automation for Expert Support
- 📞 Call/WhatsApp: +91 8802212394
- ✉ Email: jj.automation@outlook.com
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