The Fanuc 414 alarm indicates that a servo system fault has occurred.
However, this alarm does not directly identify a specific failure point.
To determine the root cause, engineers must analyze:
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CNC diagnostic data
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Servo amplifier status
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Hardware connections
-
Machine operating conditions
A comprehensive evaluation is required to accurately identify the problem.
Method for Analyzing Fanuc 414 Alarm
1. Diagnosing Using CNC Diagnostic Data
1.1 FANUC 0 Series Systems
For FANUC 0 series CNC systems, the alarm can be analyzed using diagnostic parameters:
DGN No.720 – No.727
(4n4 alarm corresponds to the nth axis servo alarm)
These diagnostic values help identify the specific fault type in the servo system.
1.2 FANUC 16/18/21, 0i-A/B/C, 16i/18i/21i-A/B Systems
For these systems, analyze the following diagnostic numbers:
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DGN No.200
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DGN No.201
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DGN No.204
These diagnostic parameters provide detailed information about the servo alarm source.
1.3 FANUC 0i-D / 0i-F / 31i / 32i / 35i Systems
Starting from the FANUC 0i-D series, the traditional 414 alarm was replaced with more specific servo alarms.
However, the troubleshooting method remains similar.
Engineers can analyze the fault through:
Servo Motor Setting Screen → Alarm 1-5
Fanuc Servo Diagnostic Code Explanation
Alarm 1 (No.720 / No.200)
| Code | Abbreviation | Description |
|---|---|---|
| #0 | OFA | Overflow alarm occurred inside the digital servo |
| #1 | FBA | Disconnection alarm – 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 abnormal current alarm – check LED |
| #5 | OVC | Digital servo overcurrent alarm |
| #6 | LV | Servo amplifier low voltage |
| #7 | OVL | Overload alarm – check diagnostic No.201 |
Alarm 2 (No.201)
When OVL = 1 in diagnostic No.201./Alarm 1, the overload alarm detail is shown below.
| ALD | EXP | Description |
|---|---|---|
| 0 | - | Motor overheating |
| 1 | - | Amplifier overheating |
When FBA = 1 in Alarm 1, the disconnection alarm details appear in diagnostic No.201.
| ALD | EXP | Description |
|---|---|---|
| 1 | 0 | Built-in pulse encoder disconnection (hardware) |
| 0 | 1 | External pulse encoder disconnection (hardware) |
| 1 | 1 | Pulse encoder disconnection (software) |
Alarm 3
| Code | Abbreviation | Description |
|---|---|---|
| #0 | SPH | Serial pulse encoder or feedback cable abnormal |
| #1 | CKA | Serial pulse encoder abnormal |
| #2 | BZA | Battery voltage dropped to 0 |
| #3 | RCA | Serial pulse encoder abnormal |
| #4 | PHA | Encoder or feedback cable abnormal |
| #5 | BLA | Battery voltage low (warning) |
| #6 | CSA | Serial pulse encoder hardware abnormal |
Alarm 4
| Code | Abbreviation | Description |
|---|---|---|
| #4 | PRM | Illegal parameter detected in digital servo (check DGN 352) |
| #5 | STB | Serial pulse encoder communication abnormal |
| #6 | CRC | Serial pulse encoder communication abnormal |
| #7 | DTE | Serial pulse encoder communication abnormal |
Alarm 5 (No.204)
| Code | Abbreviation | Description |
|---|---|---|
| #3 | PMS | Encoder or feedback cable abnormal |
| #4 | LDA | Encoder LED abnormal |
| #5 | MCC | Servo amplifier magnetic contactor stuck |
| #6 | OFS | A/D conversion abnormal in digital servo current |
⚠ Note
The above diagnostic information should be used as reference indicators.
The final fault determination should also consider:
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Hardware connections
-
Machine operating conditions
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Failure patterns
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Environmental factors
Method 2: Check Servo Amplifier LED Status
Another effective way to diagnose the Fanuc 414 alarm is by checking the LED display on the servo amplifier.
When the LED display shows a number other than “0”, it indicates that the amplifier has detected a fault.
Technicians should refer to the following manuals for detailed interpretation:
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B-65285EN – αi Series Servo Motor Maintenance Manual
-
B-65325EN – βi Series Servo Motor Maintenance Manual
These manuals provide detailed explanations for amplifier LED alarm codes and troubleshooting procedures.
Practical Troubleshooting Tips
When troubleshooting Fanuc 414 servo alarms, engineers should follow this order:
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Check CNC diagnostic parameters
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Observe servo amplifier LED status
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Inspect encoder and feedback cables
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Verify servo motor temperature
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Check power supply and amplifier voltage
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Inspect hardware connections
A systematic approach helps reduce machine downtime and ensures accurate fault identification.
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-
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-
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-
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Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC.
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