The Fanuc 0i-Model C (0i-C / 0i Mate-C) is an earlier-generation controller that displays alarms as plain numeric codes (without the letter prefixes used on the later 0i-D). Below are the alarms technicians see most often, with causes and fixes.
How Fanuc 0i-C Alarm Codes Work
On the 0i-C, alarms appear as a number and a short message on the ALARM screen. The number ranges roughly map to:
- 000–099 — Program / parameter / setting alarms
- 300–399 — Absolute Pulse Coder (APC / encoder) alarms
- 400–499 — Servo alarms
- 500–599 — Overtravel (stroke limit) alarms
- 700–749 — Overheat / spindle alarms
- 900+ — System / watchdog (PCB) alarms
Program / Parameter Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| 000 | Please turn off power | A parameter requiring a power cycle was set. Turn the machine OFF then ON. |
| 090 | Reference return incomplete | Zero return could not complete — start farther from the reference point, or check the encoder/one-rotation signal. |
| 100 | Parameter write enable | PWE = 1 on the SETTING screen. Set PWE = 0 and press RESET. |
Servo Alarms (400 Series)
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| 401 | Servo amplifier VRDY (ready) OFF | Amplifier not ready — check DC link voltage, E-stop circuit, amplifier power and fault LED. Repair/replace the servo drive if faulty. |
| 404 | VRDY signal ON (stuck) | Ready signal stays on incorrectly — usually a faulty servo amplifier or wiring. |
| 410 | Excessive position error at stop | Mechanical bind, low gain, or amplifier/motor fault while stationary. |
| 411 | Excessive position error during move | Overload, encoder fault or amplifier issue during motion. |
| 414 | Digital servo system fault | Servo detection error — check the amplifier alarm code, motor and encoder feedback. |
| 417 | Illegal digital servo parameter | Servo parameters wrong/corrupted (often after battery loss). Restore from backup; replace the CNC battery A98L-0031-0025. |
Overtravel, Overheat & Spindle Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| 500 / 501 | Stored stroke limit + / − exceeded | Axis past the soft limit. Jog back inside the range and reset. |
| 510 / 511 | Stroke limit (check before move) | Programmed move would exceed limits. Correct the program or work offset. |
| 700 | Overheat: control unit | Cabinet too hot — check the cabinet/control cooling fan and ambient temperature. |
| 704 | Spindle speed fluctuation / overheat | Spindle could not hold commanded speed or overheated — check load, belt, motor and spindle amplifier. |
Encoder (APC) & Communication Alarms
| Alarm | Meaning | Common Cause & Fix |
|---|---|---|
| 300 | APC alarm — reference return required | Absolute position lost (battery change). Perform the zero-return / referencing procedure. |
| 301 / 308 | APC communication / battery alarm | Encoder serial fault or low APC battery. Replace the encoder battery and check the cable. |
| 085 / 086 / 087 | RS-232 reader/punch error | Baud rate, framing or cable mismatch during transfer. Match settings on both devices. |
| 920 / 930 | Watchdog / CPU (system) alarm | Main board or RAM fault. Re-seat boards; if it persists the CPU/main board may need repair or replacement. |
Need the Part — or a Repair?
When a 0i-C alarm points to a failed servo amplifier, encoder, board or power supply, JJ Automation stocks new and tested used/refurbished Fanuc spares — all 100% checked before dispatch — plus board-level repair.
- 🛒 Browse Fanuc 0i-C parts, servo drives and PCB boards
- 📞 Call / WhatsApp: +91 8802212394
- ✉ Email: jj.automation@outlook.com
- 🌐 www.jjautomation.in
This is a quick-reference of commonly encountered alarms. For the complete official code list, always refer to the Fanuc 0i-C Maintenance Manual.