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Lock out and tag out all power sources to the machine following safety protocols.

HIGH VOLTAGE PRESENT - Ensure all power is disconnected and verify with meter before proceeding

Locate the spindle magnetic contactor (MC) in the electrical cabinet, typically labeled SPM, MC, or similar near the spindle drive module.

Visually inspect contactor for burn marks, pitting on contacts, or physical damage. Manually check if the contactor armature moves freely when power is off.

Use a multimeter to check continuity of auxiliary contacts (typically terminals A1-A2 or 13-14). Verify they change state when contactor is manually operated. Replace contactor if contacts are worn or feedback contacts are faulty.

Lock out and tag out all power. Reference the machine electrical schematic to identify the MCF signal wire routing from contactor to spindle amplifier.

HIGH VOLTAGE PRESENT - Verify power isolation before touching any wiring

Check MCF signal connections at both the contactor auxiliary terminal block and the spindle drive input terminal (commonly labeled MCFB, MCF, or X-contact input).

Inspect wire integrity along the entire cable run for pinch points, cable damage, or broken wires at connector crimps. Check for loose terminals or corroded connections.

Perform continuity test from contactor auxiliary contact through the entire wire path to the spindle drive input. Repair or replace damaged wiring and ensure secure connections at all termination points.

Access spindle parameters and verify parameter 4020 (contactor check time) is set appropriately, typically 200-500ms. Check parameter 4021 to confirm MCF signal check is enabled (usually set to 1).

With power on and machine in emergency stop, access spindle drive diagnostics screen and monitor the MCF input signal status (typically shown as digital input DI or X-signal status).

While observing the diagnostic screen, manually close the spindle contactor using the coil terminals (apply appropriate control voltage) and verify the drive recognizes the MCF signal change.

Apply only the rated coil voltage (typically 24VDC or 100-200VAC) to contactor coil terminals

If signal does not register at drive despite confirmed contactor closure, suspect failed drive input circuit. Contact Fanuc service for drive PCB diagnostics or replacement. If parameters are incorrect, restore to OEM settings or verify against documentation.