The FANUC SP9004 alarm indicates a power phase loss or fuse blown alarm. The related amplifier alarm number is 04. This alarm occurs when the system detects an abnormal condition in the common power supply input, such as phase loss, abnormal power frequency, or unbalanced input power.
In a FANUC spindle drive system, the common power supply must receive stable and balanced input power. If one phase is missing, the input voltage is unstable, the main power terminal is loose, the MCC contactor does not work correctly, or the power supply detection circuit is abnormal, the system may generate the SP9004 alarm.
SP9004 should be checked from the input power side first. Before replacing the common power supply module, confirm the main circuit voltage, phase loss condition, main power cable terminals, MCC contactor, CX48 wiring, external power supply stability, and special spindle winding switching conditions.
Quick Summary of FANUC SP9004 Alarm
| Alarm Code | SP9004 |
|---|---|
| Alarm Meaning | Power Phase Loss / Fuse Blown |
| Amplifier Alarm No. | 04 |
| Main Cause | Input power abnormality is detected in the common power supply. |
| Typical Power Issues | Phase loss, abnormal power frequency, unbalanced input power, unstable supply voltage |
| Main Check Items | Main circuit voltage, input power terminal, MCC contactor, MCC control circuit, CX48 wiring, external power supply voltage, high/low winding switching |
| Possible Final Cause | Common power supply module detection circuit fault |
What Does FANUC SP9004 Alarm Mean?
SP9004: Power Phase Loss / Fuse Blown
The FANUC SP9004 alarm means that the common power supply has detected an input power abnormality. This may include phase loss, abnormal power frequency, unbalanced power, or a power input condition that does not meet the required specification.
The system needs stable three-phase input power to operate the spindle amplifier correctly. If the input power is missing one phase or the voltage is unbalanced, the common power supply may not operate normally and the spindle amplifier may report alarm number 04.
This alarm is usually related to the power input side, but if all external power checks are normal, the common power supply module itself may have an internal detection circuit fault.
Common Causes of FANUC SP9004 Alarm
1. Common Power Supply Input Phase Loss
The most direct cause of SP9004 is phase loss in the common power supply input.
If one phase of the three-phase input is missing, the common power supply cannot receive balanced power. Measure the main circuit input voltage and confirm whether all phases are present.
2. Abnormal Input Power Frequency
Input power frequency abnormality may also trigger this alarm.
If the power supply frequency is unstable or outside the acceptable range, the common power supply may detect an abnormal input condition.
3. Unbalanced Input Power
If the three-phase input voltage is severely unbalanced, SP9004 may occur.
Check the voltage between each phase and confirm whether the external power supply is stable and balanced.
4. Loose Main Power Cable Terminal
Loose input power terminals may cause intermittent phase loss or voltage drop.
Check whether the main power cable terminals on the power supply module are tightened securely. Loose screws, poor contact, or damaged terminals may cause unstable input power.
5. MCC Contactor or Control Circuit Problem
The MCC contactor in the main power circuit must operate normally.
If the MCC contactor does not close correctly, has poor contact, or if its control circuit is abnormal, the common power supply may not receive stable main power.
6. External Power Supply Voltage Instability
If the equipment’s external power supply voltage is unstable, SP9004 may occur even when the internal wiring appears normal.
Measure the external supply voltage and confirm whether it remains stable during power-on, emergency stop release, and spindle operation.
7. CX48 Wiring Problem
CX48 wiring should be checked when troubleshooting SP9004.
If the CX48 wiring is incorrect, loose, or inconsistent with the required power input condition, the system may detect an abnormal power phase condition.
8. High/Low Winding Switching Issue
For spindle motors with high/low winding switching, incorrect switching may cause power or spindle drive abnormalities.
Check whether the winding switching sequence and related wiring are correct, especially if the alarm appears after spindle speed range switching, wiring maintenance, or motor replacement.
9. Common Power Supply Module Detection Circuit Fault
If the main input voltage, phase condition, MCC contactor, CX48 wiring, and external power supply have all been checked but SP9004 remains, the common power supply module may be faulty.
In this case, the internal detection circuit of the power supply module may be abnormal, and the common power supply module should be replaced.
How to Troubleshoot FANUC SP9004 Alarm
When troubleshooting SP9004, start from the power input side and then move toward the power supply module.
You may need to check:
- Whether amplifier alarm number 04 is displayed
- Whether the main circuit voltage of the power supply module is normal
- Whether the input power has phase loss
- Whether the input power frequency is abnormal
- Whether the three-phase input voltage is balanced
- Whether the main power cable terminals are tightened securely
- Whether the MCC contactor closes normally
- Whether the MCC contactor contacts are burned, worn, or have poor contact
- Whether the MCC control circuit is normal
- Whether the external supply voltage is stable
- Whether CX48 wiring is correct and firmly connected
- Whether high/low winding switching is correct for applicable spindle motors
- Whether the common power supply module detection circuit is faulty
Recommended Solution
The correct solution for FANUC SP9004 depends on whether the alarm is caused by input phase loss, unstable power supply, loose terminals, MCC contactor failure, CX48 wiring, winding switching issue, or common power supply module failure.
1. Measure the Main Circuit Input Voltage
First, measure whether the main circuit voltage supplied to the power supply module is normal.
Confirm whether all phases are present and whether the input voltage is within the required range. If there is phase loss, correct the input power supply before restarting the machine.
2. Check Whether the Power Supply Is Balanced
Check whether the three-phase input voltage is balanced.
If the power supply is unbalanced or the frequency is abnormal, the external power source should be corrected before replacing the power supply module.
3. Check Main Power Cable Terminals
Check whether the main power cable terminals on the power supply module are tightened.
Loose terminals may cause intermittent phase loss, voltage drop, heating, or poor contact. Tighten the terminals and inspect for burn marks or damaged terminals.
4. Check the MCC Contactor and Control Circuit
Confirm whether the main power MCC contactor works normally.
Check whether the contactor pulls in correctly, whether the main contacts are in good condition, and whether the MCC control circuit operates normally.
5. Check External Supply Voltage Stability
Measure the external supply voltage of the equipment.
Confirm whether the voltage remains stable during power-on, emergency stop release, and spindle operation. If the voltage fluctuates too much, improve the external power supply condition.
6. Check CX48 Wiring
Check the CX48 interface wiring condition.
Confirm whether the CX48 wiring is correct, firmly connected, and consistent with the machine wiring requirement. Poor or incorrect CX48 wiring may cause the system to detect a power input abnormality.
7. Check High/Low Winding Switching If Applicable
If the spindle motor uses high/low winding switching, check whether the winding switching is correct.
Incorrect winding switching may cause abnormal spindle drive operation and may contribute to SP9004-related power abnormalities.
8. Replace the Common Power Supply Module If the Alarm Remains
If the input voltage, phase condition, terminal connection, MCC contactor, CX48 wiring, and external power supply have all been checked but SP9004 still appears, the common power supply module may have an internal detection circuit fault.
In this case, replace the common power supply module and test again.
If your machine shows FANUC SP9004 power phase loss or fuse blown alarm, please contact REACO CNC directly. Our team can help check amplifier alarm 04, common power input voltage, phase loss, MCC contactor, CX48 wiring, winding switching condition, and common power supply module replacement options.
REACO CNC Support for FANUC SP9004 Alarm
REACO CNC provides support for FANUC CNC systems, common power supply modules, spindle amplifiers, power input circuits, MCC contactors, and related CNC hardware problems.
We can help with:
- FANUC CNC alarm analysis
- FANUC SP9004 alarm troubleshooting
- Amplifier alarm No.04 checking
- Common power supply phase loss analysis
- Main circuit input voltage checking guidance
- Input power imbalance analysis
- Main power cable terminal inspection
- MCC contactor and control circuit checking
- CX48 wiring checking support
- High/low winding switching issue checking
- Common power supply module replacement support
- Replacement FANUC CNC parts supply
If you are not sure whether the SP9004 alarm is caused by phase loss, abnormal power frequency, unbalanced input power, loose main power terminals, MCC contactor failure, CX48 wiring issue, high/low winding switching problem, or common power supply module failure, you can send us the CNC system model, alarm screen, common power supply model, spindle amplifier model, input voltage measurement, MCC contactor photos, and CX48 wiring photos. Our team will help check the possible cause.
FAQ About FANUC SP9004 Alarm
What is FANUC SP9004 alarm?
FANUC SP9004 alarm means power phase loss or fuse blown. The related amplifier alarm number is 04. It occurs when the common power supply detects an input power abnormality.
What causes FANUC SP9004 power phase loss alarm?
The alarm may be caused by input power phase loss, abnormal power frequency, unbalanced three-phase power, loose main power cable terminals, MCC contactor problems, CX48 wiring issues, external supply voltage instability, high/low winding switching problems, or common power supply module detection circuit failure.
What should I check first when SP9004 appears?
First, measure the main circuit voltage supplied to the power supply module and confirm whether there is phase loss or unbalanced input power.
Can a loose power terminal cause SP9004?
Yes. Loose main power terminals may cause poor contact, intermittent phase loss, or voltage drop, which can trigger SP9004.
Can the MCC contactor cause SP9004?
Yes. If the MCC contactor does not close properly, has poor contact, or its control circuit is abnormal, the common power supply may detect input power abnormality.
Should CX48 wiring be checked for SP9004?
Yes. CX48 wiring should be checked to confirm whether it is correct, firmly connected, and consistent with the machine wiring requirement.
Why should high/low winding switching be checked?
For spindle motors with high/low winding switching, incorrect winding switching may cause spindle drive abnormalities and should be checked during SP9004 troubleshooting.
When should the common power supply module be replaced?
If the input voltage, phase condition, main power terminals, MCC contactor, external supply voltage, CX48 wiring, and winding switching have all been checked but the alarm remains, the common power supply module may have an internal detection circuit fault and should be replaced.
How can I fix FANUC SP9004 alarm?
Measure main circuit input voltage, check for phase loss and power imbalance, tighten main power terminals, check the MCC contactor and control circuit, confirm external supply voltage stability, inspect CX48 wiring, check high/low winding switching if applicable, and replace the common power supply module if all external checks are normal.
Need Help with FANUC SP9004 Alarm?
If your CNC machine has a FANUC SP9004 power phase loss or fuse blown alarm, please contact REACO CNC. We can help analyze the alarm cause and provide suitable FANUC CNC repair, common power input checking, phase loss troubleshooting, MCC contactor inspection, CX48 wiring support, high/low winding switching checking, or common power supply module replacement support.
Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC. For More Fanuc CNC repair Cases and technical articles, please back to Fanuc Technical Support Center.
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