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Check the automatic lubrication system operation - verify grease pump cycles, pressure gauge readings, and delivery lines for blockages or leaks.

Inspect spindle grease reservoir level and refill with manufacturer-specified grease if low. Verify grease type matches OEM specifications.

Never mix different grease types - purge old grease completely if changing brands or formulations.

Manually rotate the spindle by hand (with drive disabled) to feel for roughness, grinding, or resistance indicating bearing damage or grease contamination.

Lock out machine power and verify spindle brake is released before manual rotation.

If lubrication system is functioning, perform grease purge cycle per OEM procedure to remove old or contaminated grease, then relubricate with fresh grease.

Verify coolant flow through spindle motor jacket - check flow rate, inlet/outlet temperatures, and coolant level in the chiller tank.

Inspect chiller operation - confirm compressor runs, check refrigerant pressures, clean condenser fins, and verify target coolant temperature setpoint (typically 20°C).

Check coolant pump operation and inspect hoses for kinks, blockages, or air locks. Verify flow switch operation if equipped.

Clean or replace spindle motor cooling fan and verify airflow is unobstructed around motor housing if air-cooled design.

Access spindle parameters and check current bearing temperature readings (check parameters 4061-4064 or diagnosis screen). Compare to ambient - readings above 200°C or below -20°C indicate sensor failure.

Measure resistance of each bearing temperature sensor at the spindle amplifier connector with spindle at room temperature. PT100 should read ~100Ω at 0°C, thermistors typically 1-10kΩ depending on type.

Disconnect connector from amplifier before measuring to avoid damaging drive circuits.

Inspect temperature sensor cable routing from spindle motor to amplifier for damage, pinching, coolant contamination, or proximity to high-voltage cables causing interference.

If sensor readings are erratic or out of range, replace the faulty temperature sensor or cable assembly. Reset alarm and verify stable temperature readings during test run.

Use only OEM-specified sensors with correct temperature coefficient to ensure accurate monitoring.