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Power down the machine completely and lock out main power supply following proper LOTO procedures. Wait at least 5 minutes for capacitor discharge before opening any amplifier or power supply cabinet doors.

High voltage remains present in PSM/PSMR modules for several minutes after power-off. Risk of electrocution or arc flash injury.

Locate the external radiator fan unit on the PSM/PSMR module (typically mounted on cabinet side or rear panel). Visually inspect fan blades for physical damage, debris accumulation, or blockage. Check if fan rotates freely by hand.

Inspect fan wiring harness connector at both fan motor and PSM/PSMR module. Verify connector CN1 or fan connector is fully seated and pins are not damaged or corroded. Check for broken wires or signs of overheating on insulation.

If fan is defective, replace with Fanuc OEM replacement part (reference PSM/PSMR model and specification plate for correct part number). After replacement, power up and verify alarm clears. Monitor amplifier LED for AL (red) indication, which should extinguish if fan operates correctly.

Power down and LOTO the machine. After proper discharge time, access the PSM/PSMR module and locate fan connector terminals. Using a digital multimeter, measure DC voltage at fan connector while powered off (check for short circuits to ground).

Do not measure voltage while powered on unless qualified and using proper PPE. High voltage present in PSM modules.

If safe to do so with cabinet open and proper precautions, temporarily power up the PSM/PSMR and measure fan supply voltage at connector (typically 24VDC or 200VAC depending on fan type). Compare against PSM/PSMR specification manual voltage specifications.

Only perform live voltage measurements if trained and authorized. Use insulated tools and wear arc-rated PPE.

Check DIAGNOSIS screen > SYSTEM > PMC SIGNAL for fan status bit if available on your control series (30i/31i/32i may display fan feedback). Navigate to DIAGNOSIS > SERVO > AMP to check for additional PSM fault codes or temperature warnings.

If fan power circuit is confirmed faulty but fan motor tests good, the PSM/PSMR module requires repair or replacement. Contact Fanuc service or authorized repair center. Document PSM model number, serial number, and all diagnostic findings for service report.

With machine powered down and LOTO applied, visually verify fan actually rotates during power-up sequence. You may need qualified assistance to briefly power up while observing. If fan visibly rotates but alarm persists, feedback circuit is suspect.

Check fan connector for all pins including feedback signal wires (typically separate from power wires on intelligent fans). Measure continuity of feedback signal wires from fan to PSM/PSMR control board. Damaged or broken feedback wires will cause false alarm.

If fan has integrated tachometer or Hall sensor, test sensor output using oscilloscope or frequency meter while fan runs (advanced troubleshooting). Absence of pulse signal indicates failed sensor requiring fan assembly replacement.

Review any recent parameter changes or maintenance work. Check Parameter 8132 (if applicable to your system) for PSM alarm masking or fan monitoring settings. Restore default if modified. Clear alarm history and power cycle to reset detection circuit.