What causes Fanuc error Alarm 1?

Physical disconnection of phase A/B signals from the encoder.. The encoder cable is unplugged or broken.. Internal hardware fault within the encoder's A/B signal path.. Loose wiring at the encoder connector or the controller input.

How do you fix Fanuc fault code Alarm 1?

1. Check whether the phase A/B detector is connected correctly.

Alarm 1

Hardware Disconnection (Separate Phase A/B)

Fanuc · Alpha i Series Servo Amplifier

What does Alarm 1 mean?

This alarm is issued when the separate phase A/B scale is used. It indicates a hardware disconnection related to the phase A/B detector.

Common Causes

Physical disconnection of phase A/B signals from the encoder.
The encoder cable is unplugged or broken.
Internal hardware fault within the encoder's A/B signal path.
Loose wiring at the encoder connector or the controller input.

Repair Steps & Checklist

Click steps to track your progress.

1
Check whether the phase A/B detector is connected correctly.

Browse all codes in this manual (101)

Verified technical data. Last updated: April 2026

Source: Fanuc Alpha i Series Servo Amplifier

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Hardware Disconnection (Separate Phase A/B)

What does Alarm 1 mean?

Hardware Disconnection (Separate Phase A/B)

What does Alarm 1 mean?

Common Causes

Repair Steps & Checklist

Related Faults