Guide · Fanuc · CNC spindle · Updated November 2026
Fanuc αi SPM spindle amplifier alarm codes: meaning and first checks
The αi SPM spindle amplifier shows a number on its display when it detects a fault. This guide lists common alarm numbers with their usual meaning and where to look first: amplifier, motor or cable. Star Automations repairs Fanuc spindle amplifiers and spindle motors and is an independent repairer, not a FANUC authorised service provider.
First checks before any repair
- Note the number on the amplifier display and the status LEDs, and photograph them.
- Check the amplifier model (SPM, SPM-HV or other) and the motor model from the nameplates.
- Check cooling: heat sink, fans, filters and cabinet temperature.
- Check cables and connectors on the feedback and CNC link for damage or loose pins.
- Isolate power and wait until the DC link charge indicator is out before opening anything.
Common αi SPM alarm numbers
| No. | Usual meaning | First area to check |
|---|---|---|
| 01 | Motor overheating | Motor temperature, cooling fan, load and duty cycle |
| 02 | Excessive speed deviation | Load, acceleration settings, motor and cable |
| 03 | DC link fuse blown | Amplifier power section; do not just replace the fuse |
| 04 | Input fuse blown | Input power side and amplifier |
| 05 | Control power supply fault | Amplifier control power |
| 07 | Excessive speed | Speed command, parameters and feedback |
| 08 | Input voltage too high | Incoming supply and power supply module |
| 09 | Excessive load on main circuit | Heat sink cooling, load and amplifier |
| 10 | Input voltage too low | Incoming supply and power supply module |
| 11 | DC link overvoltage | Regeneration, power supply module, braking |
| 12 | DC link overcurrent | Power module and motor winding insulation |
| 18 | Program ROM checksum error | Amplifier control board |
| 24 | Serial transfer data error | CNC link cable, noise and earthing |
| 27 | Position coder signal disconnected | Position coder cable and connector |
| 29 | Short-time overload | Load, cutting conditions and cooling |
| 31 | Speed detection signal disconnected, or motor restrained | Speed feedback cable, motor and mechanical restraint |
| 33 | Insufficient DC link charging | Charging circuit and power supply module |
| 34 | Parameter value outside allowed range | Parameters after a board or motor change |
| 36 | Error counter overflow | Feedback, mechanical load and parameters |
| 37 | Speed detector parameter setting error | Speed detector parameters |
| 41 | Position coder one-rotation signal detection failure | Position coder, cable and mounting |
| 42 | Position coder one-rotation signal not detected | Position coder, cable and mounting |
| 47 | Position coder signal abnormality | Position coder and cable |
| 51 | DC link undervoltage | Incoming supply and power supply module |
| 54 | Overload current | Load and amplifier |
| 56 | Cooling fan error | Amplifier cooling fan |
Meanings are summarised from published FANUC alarm lists. Your amplifier series and software version may differ. Confirm in the FANUC αi series amplifier descriptions manual (B-65282EN).
Amplifier, motor or cable?
Feedback alarms (27, 31, 41, 42, 47)
Usually point to the position coder or speed sensor signal. Test the cable and connector first, then the sensor and its mounting.
Power alarms (03, 04, 09, 11, 12, 30, 33)
Usually point to the amplifier power section or incoming supply. Measure supply and check insulation of the motor winding before a second power-up.
Thermal and load alarms (01, 02, 29, 56)
Usually point to cooling, fan, load or duty. Fix the cause before resetting.
Communication and memory (13, 16, 18, 24, 25)
Usually point to the CNC link cable, noise, earthing or the amplifier control board.
Fanuc spindle repair at Star Automations
Send the amplifier or spindle motor with the alarm number and nameplate. We test the unit, find the fault, repair it and bench-test before return. See Fanuc servo drive and amplifier repair, CNC spindle motor repair and Fanuc alpha amplifier and power supply spares. Machines in Bengaluru: Fanuc drive repair, Bengaluru.
Fanuc spindle alarm questions
What does a Fanuc spindle amplifier alarm number mean?
The number shown on the αi SPM display identifies the fault the amplifier detected, such as overheating, an overcurrent, a feedback signal problem or a communication error. Confirm the meaning for your exact amplifier series in the FANUC αi series amplifier descriptions manual (B-65282EN).
Does a feedback alarm such as 27, 31 or 41 mean the spindle motor is bad?
Not necessarily. These alarms point to the position coder or speed sensor signal, which can also be lost through the cable, connector or mounting. Test the feedback path before replacing the motor or the amplifier.
Can I clear the alarm and keep running?
Reset only after you have found the cause. Repeated overheating, overload or DC link alarms can damage the amplifier or motor if the cause stays.
Is it safe to open the amplifier after the alarm?
Wait for the DC link charge indicator to go out and measure before touching anything. The DC link stays charged after power-off. If you are unsure, send the amplifier to a qualified repairer.
Do you repair Fanuc αi SPM spindle amplifiers and spindle motors?
Yes. Star Automations repairs Fanuc spindle amplifiers and spindle motors. Send the amplifier model and alarm number on WhatsApp or by email. Star Automations is an independent repairer and is not a FANUC authorised service provider.
Do these alarm numbers apply to other Fanuc amplifiers?
Alarm meanings differ between αi SPM, βi SVPM and older α series amplifiers. Use the manual for your series.
Send the alarm number and amplifier model.
WhatsApp a nameplate photo and the fault to +91 97866 22233, or email info@starautomations.com.