601

Power down the CNC and lock out main power. Open the servo amplifier cabinet and visually identify the affected axis inverter module based on alarm message (axis designation n). Locate the external heat sink cooling fan assembly.

Ensure complete power lockout and wait minimum 5 minutes for capacitor discharge before touching amplifier components. Verify with multimeter that DC bus voltage is 0V.

Manually attempt to rotate the fan blade. Check for bearing seizure, accumulated debris, or foreign object obstruction. Inspect fan connector CN** at the amplifier module for proper seating and damaged pins.

Do not force seized fan bearings as fragments may enter the amplifier. Replace entire fan assembly if resistance detected.

With power restored, navigate to DIAGNOSIS screen > SYSTEM > PMC > I/O LINK or SERVO screen to observe fan status signals. For αi series amplifiers, check diagnostic address X***.* for fan feedback bit specific to axis amplifier module.

Replace fan assembly with Fanuc OEM part number (typically A90L-0001-05** series for αiSV amplifiers). Verify fan voltage rating matches amplifier specification (typically 24VDC or 200VAC). Clear alarm with RESET, cycle power, and verify fan rotation and alarm does not return.

Using non-OEM fans may result in incorrect airflow rating or tachometer signal incompatibility causing repeat alarms.

With power locked out, disconnect the fan connector from the amplifier at CN** connector. Using multimeter, check continuity of fan wiring harness from amplifier to fan motor. Look for pinched cables, thermal damage, or connector corrosion.

Check wiring routing for contact with sharp edges or hot surfaces that may have caused insulation breakdown.

Restore power and measure voltage at the fan connector on amplifier side: 24VDC fans should read +24VDC ±10%, 200VAC fans should read proper line voltage. If voltage absent, suspect amplifier internal fan power supply failure.

Use extreme caution measuring voltage on live amplifier terminals. Ensure meter leads are properly insulated and rated for voltage present.

If fan power supply voltage correct but fan inoperative, disconnect fan and measure fan motor resistance across power terminals (typically 20-200Ω for DC fans, higher for AC). Open circuit indicates fan motor winding failure; short circuit (<5Ω) indicates winding short requiring fan replacement.

Check amplifier LED status indicators on axis module front panel for fault codes. Refer to αiSV or βiSV amplifier hardware manual for LED blink code interpretation specific to fan circuit failures (typically alternating red/green pattern). Replace amplifier if internal fan supply circuit failed.

With fan powered and running, verify physical rotation by observation. If fan rotates but alarm persists, suspect feedback circuit fault. Check fan connector pinout diagram in servo amplifier hardware manual (A06B-6***-H*** series documentation) to identify tachometer signal pins (typically FG or TACH designation).

Using oscilloscope, probe the fan tachometer output signal while fan runs. Expected signal is pulsed DC (typically 2-12 pulses per revolution at 0-5VDC levels). Absence of pulse signal with running fan indicates failed Hall sensor or tachometer generator in fan assembly requiring fan replacement.

Navigate to DIAGNOSIS > SERVO screen. Access axis-specific servo amplifier diagnostic data at address 300-399 for αiSV or 400-499 for βiSV series. Look for fan status bits or thermal monitoring values. Abnormal readings with properly functioning fan indicate amplifier monitoring circuit fault.