How to Diagnose and Fix FANUC Alarm 414 on CNC Machines

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FANUC alarm 414 is one of the most common issues encountered on CNC machines equipped with FANUC controls. It typically indicates a servo amplifier fault related to an axis motor, often caused by hardware failure, connection issues, or internal short circuits. In this article, we will walk you through a real-world case study and show you how we successfully diagnosed and repaired a machine suffering from a FANUC alarm 414 on both the Z and B axes.

What Causes FANUC Alarm 414?

The FANUC alarm 414 generally indicates an abnormal current detected by the servo amplifier for a particular axis. It often signals serious problems within the servo drive system that must be addressed immediately.

Common causes of FANUC alarm 414

  • Defective Servo Amplifier Module:
    Internal damage to the amplifier’s circuitry can cause abnormal current detection.
  • Short Circuit in the Motor or Power Cables:
    Electrical shorts in the motor windings or power wiring can lead to sudden overcurrent situations.
  • Damaged or Improperly Connected Axis Control Cards:
    Faulty or loose 3/4 axis control card (e.g., A20B-2902-0290) connections can interfere with normal axis operations.
  • Faulty Power Supply Unit:
    Insufficient or unstable power supply output (such as from an A06B-6087-H137 unit) may trigger an overcurrent alarm in the servo system.
  • Low Input Voltage to the Servo System:
    If the input voltage to the servo drive is too low, it can cause the servo amplifier to misfire and produce a 414 alarm.
  • External Contactor Faults or Tripped Breakers:
    Malfunctioning external contactors or an open external circuit breaker can interrupt power delivery, causing abnormal servo amplifier behavior.
  • *Delayed ESP Signal Connection:
    If the *ESP (Emergency Stop Permit) signal from the internal DI system or through the I/O Link interface is not established within 190ms after the external contactor closes, the system may issue a 414 alarm.

 

Understanding and systematically diagnosing these root causes is critical to efficiently troubleshooting and repairing machines affected by fanuc alarm 414.

fanuc Alarm 414 Axis

How to Analyze FANUC Alarm 414 Across Different CNC Systems

The method for diagnosing fanuc alarm 414 can vary depending on the specific CNC system generation. Understanding which diagnostic parameters to check is essential for accurate fault analysis. Here’s a breakdown:

  1. FANUC 0 Series Systems:
    Use the Diagnostic Data (DGN) No.720–727. Each number corresponds to the 414 alarm status for a specific axis (the nth axis). By analyzing these diagnostics, the faulty axis and cause can be identified.
  2. FANUC 16/18/21, 0i-A/B/C, and 16i/18i/21i-A/B Series:
    Diagnosis should be performed by reviewing DGN No.200, No.201, and No.204. These diagnostic numbers provide detailed information on axis-specific faults that may cause a 414 alarm.
  3. FANUC 0i-D/F, 31i/32i/35i-A/B Series and Newer Systems:
    Starting from the 0i-D generation, the traditional 414 alarm was replaced by more precise servo-specific alarms. However, the methods for analyzing servo faults remain similar. Users should check the “Servo Motor Setting” screens, focusing on Alarms 1 to 5, to determine the exact cause of failure.

At the end of the article, we will provide a detailed diagnostic code interpretation table to assist in troubleshooting FANUC alarm 414 more effectively.

Case Study: FANUC 0i-MA 414 Alarm on Z and B Axis

Recently, at CNCFixtech, we were tasked with repairing a FANUC 0i-MA CNC system that triggered fanuc alarm 414 immediately after powering on. The alarm was present on both the Z axis and B axis.

Equipment Involved

Diagnostic Steps

  1. Check Axis Amplifiers:
    Using diagnostics screens 204 and 61, we verified that the axis amplifiers were functioning properly and showed no signs of failure.
  2. Inspect 3/4 Axis Card Connections:
    We then checked the connection status of the 3/4 axis card. No loose connections were found, but the FANUC 414 alarm persisted after rebooting.
  3. Replace the 3/4 Axis Card:
    We decided to replace the A20B-2902-0290 card. After replacement, the alarm was completely cleared, and the machine booted up normally.
  4. Confirm and Test:
    After the repair, the Z and B axes were tested under normal operation, and the system worked flawlessly.

How to Quickly Resolve FANUC Alarm 414

If you encounter fanuc alarm 414, here are some tips to speed up diagnosis:

  • Check if the problem affects a specific axis or multiple axes

  • Inspect the servo amplifier units for any error LEDs

  • Review connection status of axis control cards

  • Check the diagnostic pages (especially Diagnostics 204)

  • If necessary, swap suspected parts (amplifier, axis cards) one at a time

Prompt and accurate diagnosis can save valuable downtime in production environments.

FANUC Drive in lathe, fanuc alarm list pdf

Detailed explanation of diagnostic codes

【No.720/No.200/Alarm1】

#0

OFA

Overflow alarm occurs inside the digital servo

#1

FBA

Disconnection alarm occurs, check diagnostic No. 201

#2

DCA

Servo amplifier discharge circuit alarm, check LED

#3

HVA

Servo amplifier overvoltage alarm, check LED

#4

HCA

Servo amplifier current abnormality alarm, check LED

#5

OVC

Overcurrent alarm occurs inside the digital servo

#6

LV

Servo amplifier voltage is insufficient

#7

OVL

Overload alarm occurs, check diagnostic No. 201

 

【No.201/Alarm2】

When the OVL of diagnosis No.200/alarm 1 is 1

 

ALD

EXP

Content

Overload Alarm

0

/

Motor overheating

1

/

Amplifier overheating

When FBA of diagnosis No.200/alarm 2 is 1

 

ALD

EXP

Content

Disconnection Alarm

1

0

Built-in pulse encoder disconnection (hardware)

0

1

External pulse encoder disconnection (hardware)

1

1

Pulse encoder disconnection (software)

【Alarm3】

#0

SPH

Serial pulse encoder or feedback cable abnormality

#1

CKA

Serial pulse encoder abnormality

#2

BZA

Battery voltage drops to 0

#3

RCA

Serial pulse encoder abnormality

#4

PHA

Serial pulse encoder or feedback cable abnormality

#5

BLA

Battery voltage drops (warning)

#6

CSA

Serial pulse encoder hardware abnormality

【Alarm4】

#4

PRM

The digital servo side detected illegal parameters. The details are displayed in the diagnostic N0.352

#5

STB

Serial pulse encoder communication abnormality

#6

CRC

Serial pulse encoder communication abnormality

#7

DTE

Serial pulse encoder communication abnormality

【No.204/Alarm5】

#3

PMS

Serial pulse encoder or feedback cable abnormality

#4

LDA

Serial pulse encoder LED abnormality

#5

MCC

Servo amplifier electromagnetic contactor contact adhesion

#6

OFS

Digital servo current value A/D conversion abnormality

[Note] The above diagnosis is only a reference for judging the fault. Please also make a comprehensive judgment based on hardware connection, fault occurrence pattern, etc.

Conclusion

 Resolving fanuc alarm 414 requires a systematic approach to identify whether the problem lies in the servo amplifier, motor wiring, or control cards. In our case, replacing the faulty 3/4 axis card successfully restored full functionality to the FANUC 0i-MA system.

At CNCFixtech, we specialize in repairing FANUC power supply units, servo amplifiers, axis cards, and spindle drives. If you are facing issues like FANUC alarm 414, don’t hesitate to contact our professional repair team.

FAQ

What does FANUC alarm 414 mean?

FANUC alarm 414 typically indicates an abnormal current detected in the servo amplifier of a particular axis. It often points to issues such as a defective servo drive module, short-circuited motor wiring, or power supply irregularities.

Common causes include a faulty servo amplifier, short circuits in the motor or cables, improperly connected axis control cards, low input voltage to the drive system, external contactor faults, or delayed *ESP (Emergency Stop Permit) signal activation.

  • FANUC 0 Series: Analyze DGN No.720–727 for axis-specific 414 alarms.

  • FANUC 16/18/21, 0i-A/B/C, 16i/18i/21i-A/B: Use DGN No.200, 201, and 204 for troubleshooting.

  • FANUC 0i-D/F, 31i/32i/35i-A/B Series: Review servo motor setting screens (Alarm 1–5) to pinpoint faults.

Yes. Insufficient power input to the servo amplifier can lead to abnormal current detection, triggering a 414 alarm.

Not necessarily. Although a defective amplifier is a common cause, you should first perform thorough diagnostics to rule out simpler issues like loose connections, wiring faults, or external power problems before replacing major components.

➔ Need Help Fixing FANUC Alarm 414?

If you encounter persistent issues or need expert repair services for your FANUC drives and servo systems, feel free to contact our team for professional assistance!

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Step 1: Contact Us:

Get in touch with us and provide as much detail as possible about the issue you are experiencing.

Our professional repair team will help assess the severity of the problem and the possibility of repair.

  • If the fault is likely repairable, we will provide an initial quote and arrange for logistics to collect the item.
  • If the fault is difficult to repair, we will suggest replacing the parts and offer a special discount quote for your reference.

The customer sends or delivers the servo drive to our company. We register it in our system and prepare it for further inspection.

Our engineers diagnose the fault points of the servo drive and provide a detailed inspection report, including the final repair cost and estimated repair time.

We provide the repair quote to the customer and wait for their confirmation. If the customer agrees to the quote, we proceed with the repair. 

Upon customer approval, we carry out the necessary repairs. After repairs are completed, we perform tests with the motor and conduct aging tests to ensure the servo drive operates reliably under various conditions. Once the testing is successful, we register the drive for delivery.

The customer completes the payment, and we deliver the repaired servo drive to the customer.

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