FANUC SP9059 Alarm 59: Converter Cooling Fan Failure and Troubleshooting

FANUC SP9059 means that the internal cooling fan in the common Power Supply module has stopped. The CNC may display SP9059 CNV. COOLING FAN FAILURE, the spindle alarm number is 59, and the Power Supply normally displays 2.

FANUC's CNC alarm list directs technicians to replace the Power Supply. The more detailed αi amplifier maintenance procedure identifies a stopped control-circuit cooling fan as the cause of Power Supply alarm 2 and instructs technicians to check whether the fan rotates normally and replace the failed fan. On specified upgraded Power Supply models, the same alarm can also indicate a stopped internal stirring fan.

For nearby spindle alarm numbers, see the FANUC Spindle Alarm Codes SP9034–SP9092.

What Does FANUC SP9059 Mean?

SP9059 is generated when the spindle system receives a cooling-fan alarm from the common Power Supply. This module supplies the DC link used by the connected servo and spindle amplifiers, so a fan fault can stop the machine even if the spindle amplifier itself is healthy.

The three displays should be read together:

• SP9059 is the CNC alarm number.

• 59 is the corresponding spindle alarm indication.

• 2 is the Power Supply alarm indication identified by FANUC for a stopped control-circuit cooling fan.

Do not assume that every fan visible in the drive cabinet can cause SP9059. The alarm identifies the Power Supply cooling system, not the CNC cabinet fan, spindle motor fan, spindle-amplifier internal fan, or spindle-amplifier radiator fan.

Why FANUC Documentation Gives Two Repair Directions

The CNC alarm list gives a concise module-level action: replace the Power Supply. The αi amplifier maintenance manual provides a more detailed component-level procedure for Power Supply alarm 2: check the cooling fan and replace it if it does not rotate normally. It also identifies the internal stirring fan on specified upgraded Power Supply models.

These instructions are not contradictory. A qualified technician can normally confirm and replace a serviceable fan first. If the correct fan and its connection are good but alarm 2 remains, the fault may be in the fan-feedback or detection circuit, and replacement of the applicable control-board assembly or complete Power Supply may be required.

1. Confirm SP9059, Alarm 59, and Power Supply Alarm 2

Before removing parts, record all displays and the exact equipment information:

• CNC alarm text and number

• Spindle alarm indication 59

• Power Supply indication 2

• Complete Power Supply model, including every suffix and option

• CNC series and model

• Whether the alarm occurs immediately at power-up or after the machine has operated

• Any recent fan, control-board, connector, or drive maintenance

If the Power Supply displays a different code, diagnose that code instead. For example, indication 3 identifies abnormal main-circuit heat-sink temperature and belongs to SP9058, not SP9059.

2. Isolate Power Before Inspecting the Fan Assembly

The Power Supply contains hazardous voltage, and the DC link can remain charged after input power is switched off. Fan and control-board inspection must be performed only by qualified personnel using the applicable FANUC and machine-builder procedures.

Before opening the drive cabinet or withdrawing a board assembly:

1. Stop the machine according to the machine builder's procedure.

2. Isolate the main and control power sources.

3. Apply the required lockout/tagout controls.

4. Wait the specified discharge time.

5. Confirm that the DC-link voltage has fallen to a safe level using the prescribed method.

Do not insert tools into a moving fan, disconnect a fan while energized, or rely only on the Power Supply display going dark.

3. Check the Power Supply Control Board and Fan Connector

If the applicable model uses a removable control-board or side-board assembly, inspect its seating before condemning the complete Power Supply. A board that was not fully reinstalled after maintenance can leave internal connections loose. Also inspect the fan-motor connector for incomplete engagement, bent or recessed contacts, damaged conductors, contamination, or heat discoloration.

The following English diagram shows the typical release and withdrawal direction. It is a representative service illustration; the exact latches, faceplate, and board arrangement vary by Power Supply model.

How to release and remove the FANUC Power Supply control board assembly.

After withdrawing the assembly according to the correct manual, identify the fan connector and fan motor. The next diagram shows a representative control board with the fan motor, heat sink, and fuse locations.

FANUC Power Supply fan motor and FU1, FU2, and FU3 locations on the illustrated control board.

The fuse ratings and physical layout shown in the diagram apply only to the illustrated configuration. They are orientation references, not universal replacement specifications. Do not replace a fuse solely because SP9059 is present; use the electrical drawing and maintenance manual for the exact Power Supply model.

When reinstalling the assembly, make sure it is fully seated and secured. Never force a connector or use the faceplate screws to pull a misaligned board into position.

4. Check Whether the Cooling Fan Rotates Normally

FANUC's detailed Power Supply alarm 2 procedure instructs technicians to check whether the cooling fan rotates normally. With the equipment safely de-energized, inspect for:

• A blade blocked by wiring, debris, or a displaced guard

• Heavy dust or oily contamination

• Cracked, bent, or missing blades

• Bearing roughness, drag, or excessive free play

• A loose fan plug or damaged lead

• Heat damage at the connector or board

• Evidence that the fan starts intermittently or runs below normal speed

Turning the blades gently by hand can reveal a seized bearing or a mechanical obstruction, but free movement does not prove that the motor, speed-feedback signal, supply voltage, or detection circuit is healthy.

If the fan runs only after being pushed, starts slowly, stops intermittently, or produces abnormal noise, replace it. A marginal fan can restart during a brief test and still fail again after the cabinet warms up.

5. Clean Contamination Carefully, but Replace a Degraded Fan

Remove loose dust from the permitted cooling paths using the cleaning method specified by the machine builder or FANUC manual. Prevent debris from being driven farther into the Power Supply, and do not overspeed the fan with compressed air.

Cleaning may remove an external obstruction, but it does not restore worn bearings or a failed fan motor. Oil residue around the bearing area, unstable speed, rough rotation, or repeated stopping is evidence to replace the fan rather than treat cleaning as a permanent repair.

Use only the exact compatible replacement. Confirm:

• FANUC Power Supply model and all suffixes

• Fan part number and dimensions

• Rated voltage and current

• Airflow direction

• Connector type, keying, and pin assignment

• Speed-alarm or feedback lead arrangement

• Mounting direction and cable routing

A fan that fits mechanically can still have an incompatible connector, airflow direction, electrical rating, or feedback signal.

6. Check the Internal Stirring Fan on Applicable Upgraded Units

FANUC states that Power Supply alarm 2 can also be issued when the internal stirring fan stops on upgraded A06B-6140-HXXX and A06B-6150-HXXX Power Supply units. If the normal control-circuit fan is operating correctly on one of these configurations, identify and test the additional internal stirring fan using the exact unit manual.

Do not assume that every Power Supply contains this second fan. Use the complete model and suffix to determine the installed hardware and the correct replacement procedure.

7. If the Fan Rotates but SP9059 Remains

A visibly rotating fan does not rule out a fan-system fault. The Power Supply may still detect insufficient speed, a missing feedback signal, an intermittent connector, or a defective monitoring circuit.

Proceed in this order:

1. Confirm that the fan starts every time and reaches stable speed.

2. Verify that the correct fan is installed and oriented correctly.

3. Recheck the fan connector, pins, leads, and board seating.

4. Check the fan supply and feedback circuit using the model-specific procedure.

5. Substitute a known-good exact-compatible fan if permitted.

6. If alarm 2 remains, diagnose the Power Supply control board or fan-detection circuit.

7. Replace the applicable board assembly or complete Power Supply when the manual and test results identify it as faulty.

Do not bypass the fan-alarm circuit or jumper the feedback signal. That can allow the Power Supply to operate without confirmed cooling and can lead to overheating or secondary drive damage.

If a replacement Power Supply is required, browse FANUC servo, spindle, and power drives or send the complete unit model and suffix to REACO CNC for a compatibility check.

8. Retest the Power Supply and Drive System

After reinstalling the board or replacing the fan or Power Supply:

• Confirm that the board assembly and every connector are fully seated.

• Confirm the fan's airflow direction and unobstructed clearance.

• Verify that the fan starts normally at power-up under the applicable test procedure.

• Confirm that Power Supply alarm 2, spindle alarm 59, and CNC alarm SP9059 do not return.

• Run the machine through the machine builder's controlled spindle and servo test.

• Observe the fan for delayed starting, unstable speed, abnormal sound, or intermittent stopping.

• Diagnose any new alarm by its own number instead of continuing to treat it as SP9059.

Difference Between SP9056, SP9058, SP9059, and SP9088

Several FANUC alarms involve cooling, but they identify different modules or detection conditions:

The physical location of the failed fan matters. Replacing the spindle-amplifier fan will not correct SP9059 if the stopped fan is inside the common Power Supply.

FANUC SP9059 Diagnostic Table

What Not to Do

• Do not keep resetting SP9059 and operating the machine without confirmed cooling.

• Do not bypass or simulate the fan-feedback signal.

• Do not spin the fan with tools while the Power Supply is energized.

• Do not assume that a fan is healthy only because its blades move freely by hand.

• Do not install a generic fan based only on dimensions.

• Do not replace FU1, FU2, or FU3 solely because the diagram shows their locations.

• Do not replace the spindle amplifier when the confirmed alarm source is the common Power Supply.

• Do not withdraw or insert the Power Supply control board until the required power-isolation and discharge procedure is complete.

Recommended Troubleshooting Order

1. Confirm SP9059 on the CNC, 59 as the spindle alarm indication, and 2 on the Power Supply.

2. Record the complete CNC and Power Supply models, including all suffixes.

3. Isolate power, wait the specified discharge time, and verify a safe condition.

4. Confirm that the removable control-board or side-board assembly is fully seated.

5. Inspect the fan connector, leads, blades, guard, and surrounding cooling path.

6. Check whether the Power Supply control-circuit cooling fan starts and rotates normally.

7. On applicable upgraded A06B-6140-HXXX or A06B-6150-HXXX units, inspect the internal stirring fan.

8. Replace the failed fan with the exact compatible part.

9. If the correct fan and connections are good but the alarm remains, diagnose the fan-feedback and detection circuit.

10. Replace the applicable board assembly or complete Power Supply when confirmed faulty.

11. Retest the drive system and diagnose any different alarm separately.

Technical References

• FANUC Series 0i-MODEL D / Series 0i Mate-MODEL D Maintenance Manual, B-64305EN/03, SP9059 alarm list

• FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285EN/04, Power Supply Alarm Code 2

Always use the manual edition that applies to the exact CNC, Power Supply, drive series, machine, and hardware revision.

Need Help With FANUC SP9059 Alarm 59?

REACO CNC provides independent testing, repair, compatibility checking, and replacement support for FANUC Power Supply modules, drive control boards, and cooling components. Send us the CNC alarm screen, Power Supply display, complete CNC model, complete Power Supply part number and suffix, fan photos, and details of when the alarm occurs.

Visit the FANUC Technical Support Center for more FANUC alarm guides, or contact REACO CNC for assistance.

Reference Source: Beijing FANUC. This article is based on FANUC technical documentation. The exact fan location, board-removal method, part number, fuse arrangement, and replacement procedure depend on the installed Power Supply and machine configuration.