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Allow spindle motor to cool completely for at least 30 minutes before further inspection.

Inspect spindle motor cooling fan operation - verify fan runs when spindle is enabled and check for proper airflow direction.

Lockout/tagout machine before accessing electrical cabinets or motor areas.

Clean all cooling fins and air passages on spindle motor housing using compressed air, removing accumulated chips, dust, and coolant residue.

Wear safety glasses and ensure machine is powered off before using compressed air near electrical components.

Replace cooling fan if not operating or if bearing noise is present - verify correct voltage at fan connector and check fan motor continuity.

Review cutting parameters and machining cycle time before alarm occurred - identify if spindle was operating at high load for extended periods.

Check spindle load meter on CNC display during a test cut at reduced feed rate - verify load does not exceed 80% continuously.

Inspect tooling for wear or damage and verify proper tool holder balance - replace dull tools and ensure proper speeds/feeds for material being cut.

Verify through-spindle coolant or external coolant is flowing properly to reduce cutting friction and heat generation during machining.

Check spindle amplifier diagnosis screen (Maintenance > SPINDLE > ALARM or SP LOAD) for specific temperature readings and error details.

Measure thermistor resistance at spindle motor connector when cold (should be 50-500 ohms typically at room temperature) - compare to manufacturer specifications.

Disconnect motor power cables before measuring thermistor resistance to avoid damage to meter.

Inspect spindle amplifier cooling fans and heat sink for proper operation - verify amplifier cabinet temperature is within normal range (below 45°C ambient).

Check all connections between spindle motor thermistor and amplifier for loose wires, damaged connectors, or signs of overheating at terminals.

Lockout/tagout before inspecting connections in electrical cabinet.