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Power off the machine and lock out all energy sources before inspection.

HIGH VOLTAGE - Ensure complete lockout/tagout procedure is followed

Locate the AE sensor cable connected to the spindle motor housing (typically a small coaxial or shielded cable separate from power cables).

Inspect the entire cable run for physical damage, cuts, pinch points, or coolant contamination. Check both connectors at the spindle motor and amplifier for corrosion, bent pins, or looseness.

Disconnect cable at both ends and perform continuity test on all conductors and shield. Replace cable if any open circuits or short circuits are found.

With power locked out, access the AE sensor mounted on the spindle motor (consult spindle motor manual for exact location - often near front bearing housing).

Disconnect the sensor and measure resistance across sensor terminals. Typical reading should be 100-500 ohms; open circuit or short circuit indicates sensor failure.

If sensor measures out of specification, order exact replacement sensor using spindle motor model and serial number (sensor must match motor specifications).

Replace sensor ensuring proper torque specification and thermal compound application if required. Verify cable routing prevents strain on sensor connection.

Verify sensor and cable are functional by testing with known good components or measuring sensor output signal with oscilloscope during spindle operation (observe piezo signal during tap test).

Check spindle amplifier parameters: verify parameter 4035 (AE sensor enable) is set correctly and parameter 4036 (AE detection level) is not set to zero or extreme values.

Inspect spindle amplifier circuit board for visible damage, burnt components, or contamination around the AE input connector area. Check connector pins for damage.

If sensor and cable test good but alarm persists, the amplifier AE input circuit has likely failed. Contact Fanuc service for amplifier repair or replacement - this requires factory repair or board-level diagnosis.