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Check coolant tank level and verify adequate coolant supply to the spindle cooling circuit.

Inspect the flow sensor/switch connections at the spindle motor housing for loose wiring, corrosion, or damaged connectors.

Remove and inspect the flow sensor paddle or impeller for debris, damage, or restrictions. Clean or replace as needed.

Ensure coolant system is depressurized before disconnecting flow sensor components.

Test flow sensor continuity and resistance values against maintenance manual specifications. Replace sensor if readings are out of tolerance.

Verify the spindle cooling pump is running when spindle operation is commanded. Listen for pump motor operation and check for pump signal at the drive.

Inspect coolant hoses and lines for kinks, blockages, or collapsed hoses restricting flow to the spindle motor.

Check coolant filter for clogging and clean or replace filter element. Verify pressure gauges show adequate system pressure.

Wear appropriate PPE when handling coolant system components.

Test pump relay and contactor operation in the electrical cabinet. Replace pump if motor is receiving power but not operating.

Lockout/tagout electrical power before inspecting pump motor or relay connections.

Access spindle drive diagnostics and check the actual temperature reading on the spindle amp display or PMC parameters.

Locate the thermistor or PT100 temperature sensor on the spindle motor housing and inspect wiring for damage, shorts, or opens.

Measure resistance of the temperature sensor at room temperature and compare to specification (typically 100 ohms at 0°C for PT100 or ~10k ohms at 25°C for thermistor).

Allow spindle to cool completely before testing temperature sensor resistance.

If sensor readings are correct but alarm persists, check spindle drive parameter settings for temperature threshold limits and verify they match spindle motor specifications.