FANUC SP9012 means that an excessively large current has been detected in the spindle amplifier main circuit. The related spindle amplifier display is alarm 12. Depending on the amplifier series, the alarm may indicate DC link overcurrent or an IPM-detected condition such as excessive load or overcurrent.
The correct troubleshooting path depends on when the alarm appears: immediately after power-on, immediately after a spindle rotation command, during normal spindle rotation, or during winding or speed-range switching.
| Alarm location | Display | Meaning |
|---|---|---|
| CNC | SP9012 | DC link overcurrent / power circuit overcurrent |
| Spindle amplifier | 12 | Excessive current in the main circuit |
| Related check on specified amplifier models | 09 | IPM or main-circuit overheat condition |
For an overview of related spindle alarms, see the FANUC Serial Spindle Alarm Codes SP9001–SP9033.
Important Amplifier-Series Distinction
On specified lower-capacity αi spindle amplifier models, alarm 12 may indicate that the main-circuit IPM detected an excessive load, overcurrent, or related fault. FANUC instructs technicians to check alarm code 09 as well on the applicable models.
If heat sink temperature or cooling is involved, refer to the related FANUC SP9009 Main Circuit Overheat troubleshooting guide.
Always identify the exact spindle amplifier and motor model before applying a model-specific procedure.
1. If SP9012 Appears Immediately After Power-On
Check whether the control printed-circuit board on the front of the spindle amplifier is installed correctly. The board must be fully inserted. Poor contact at the connector between the control board and power circuit board may cause alarm 12.
If the board is not seated correctly, qualified maintenance personnel should remove and reinstall it according to the applicable FANUC maintenance procedure. If the board is correctly installed and the alarm remains, the spindle amplifier may require testing and replacement.
2. If SP9012 Appears Immediately After a Spindle Rotation Command
When the alarm occurs as soon as the spindle rotation command is issued, check the following areas in order.
Check the spindle motor power cable
Inspect the motor power cable for:
- A short circuit between power conductors
- A short circuit from a power conductor to ground
- Incorrect connection or phase sequence
- Damaged insulation
Replace the power cable if a short circuit, insulation failure, or other cable defect is confirmed.
Check the spindle motor winding insulation
Check whether the spindle motor winding is short-circuited to ground. If the motor winding insulation has failed, replace the spindle motor according to the applicable FANUC procedure.
Before replacing the spindle amplifier, FANUC instructs technicians to verify the insulation condition of both the motor power cable and the motor winding.
Check the motor-specific parameters
Identify the exact spindle motor model and verify that the motor-specific parameters are correct. Refer to the applicable FANUC AC Spindle Motor Parameter Manual B-65280CM.
If the parameter data is incorrect or uncertain, initialize the spindle motor parameters using the correct motor model and configuration, then test the spindle again. Related checks involving motor parameters, power cables, and speed feedback are also described in the FANUC SP9002 Excessive Spindle Speed Deviation guide.
Check the spindle amplifier
If the power cable, motor insulation, and motor-specific parameters are all normal but SP9012 remains, a spindle amplifier power element such as the IGBT or IPM may be damaged. Professionally test the spindle amplifier and replace it if the fault is confirmed. An independent repair provider may also evaluate whether the failed unit is repairable.
3. If SP9012 Appears During Normal Spindle Rotation
If the spindle starts normally but alarm 12 appears while it is rotating, use the following checks.
Verify the motor-specific parameters
Confirm the spindle motor model and check its inherent parameters against the correct FANUC parameter manual. Reinitialize the parameters when required.
Check the spindle sensor and sensor cable
Inspect the spindle sensor and its cable. Where suitable test equipment and the applicable FANUC procedure are available, monitor the spindle sensor signal waveform.
If the waveform is abnormal, adjust the sensor installation or replace the spindle sensor as required.
Check power-cable and motor-winding continuity
Check the continuity of the spindle motor power cable and motor winding. Replace the defective cable or motor if an open circuit or another electrical abnormality is confirmed.
Check for belt slippage on applicable βiIc motors
For the FANUC βiIc spindle motor series only, belt slippage between the spindle and motor may cause SP9012. Clean the pulleys and readjust the belt tension so the belt does not slip.
This cause is model-specific and should not be applied to other spindle motor series without confirmation from the corresponding FANUC manual.
Check amplifier cooling and installation conditions
Insufficient cooling or operation outside the spindle amplifier installation specifications may damage the internal power elements.
Check whether the heat sink is dirty and whether the cabinet provides sufficient cooling. Clean the heat sink using the method specified in the maintenance documentation and ensure that coolant does not directly reach the heat sink area. Also confirm that the spindle amplifier installation and operating conditions comply with the applicable FANUC specifications.
If a power element has already failed, the spindle amplifier must be repaired or replaced. Cooling and installation problems should also be corrected to prevent recurrence.
4. If SP9012 Appears During Winding or Speed-Range Switching
If the machine uses spindle high/low winding switching, output switching, or speed-range switching and SP9012 occurs during the switching operation, check:
- The magnetic contactor used for spindle power-lead or winding switching
- The contactor power supply and contact operation
- The related wiring and feedback signals
- The PMC or ladder switching sequence
- The parameters associated with spindle switching
The contactor and PMC sequence must switch the spindle circuit in the correct order. A contactor fault, wiring error, or incorrect switching sequence can create an abnormal current condition.
This section applies only to machines equipped with the corresponding spindle switching function.
FANUC SP9012 Diagnostic Table
| When the alarm occurs | Main check direction | Recommended action |
| Immediately after power-on | Control board installation or amplifier fault | Reseat the board correctly; test the amplifier if the alarm remains |
| Immediately after a rotation command | Power-cable short circuit, motor insulation failure, parameter error | Check cable insulation, motor winding, phase sequence, and motor-specific parameters |
| During normal rotation | Parameter, sensor, continuity, cooling, or power-element problem | Check parameters, sensor waveform, cable and winding continuity, heat sink, and amplifier |
| During βiIc spindle rotation | Possible belt slippage | Clean pulleys and adjust belt tension |
| During winding or speed-range switching | Contactor, wiring, PMC sequence, or switching parameter problem | Check the switching hardware, signals, sequence, and parameters |
| All external checks are normal | Spindle amplifier power element fault | Professionally test, repair, or replace the spindle amplifier |
Recommended Troubleshooting Order
- Record exactly when SP9012 occurs.
- Identify the spindle amplifier and spindle motor models.
- Check whether the control board is fully installed.
- Check motor power-cable insulation, grounding, connection, phase sequence, and continuity.
- Check spindle motor winding insulation and continuity.
- Verify or initialize the motor-specific parameters.
- If the alarm occurs during rotation, check the sensor signal, cooling condition, and applicable belt condition.
- If the alarm occurs during winding switching, check the contactor and PMC sequence.
- Test the spindle amplifier and repair or replace it only after the external checks are completed.
Technical References
- FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285 series
- FANUC AC Servo Motor βi Series, AC Spindle Motor βi Series, Servo Amplifier βi Series Maintenance Manual, B-65325 series
- FANUC AC Spindle Motor αi/βi Series Parameter Manual, B-65280CM
- FANUC Servo Amplifier αi Series Descriptions, B-65282 series
Always use the manual edition that applies to the exact CNC, spindle motor, spindle amplifier, and machine configuration.
Need Help With FANUC SP9012 Alarm?
REACO CNC provides independent testing, repair, and replacement support for FANUC spindle amplifiers and spindle motors. Send us the CNC alarm screen, amplifier LED display, exact spindle amplifier model, spindle motor model, and a description of when the alarm occurs.
Visit the FANUC Technical Support Center for more FANUC alarm guides and repair information, or contact REACO CNC for technical support.
Reference Source: Beijing FANUC. This article is based on FANUC technical documentation. The applicable manual and procedure depend on the exact CNC, spindle amplifier, spindle motor, and machine configuration.
