Fanuc spindle alarm 85 means the one-rotation signal of the SPINDLE sensor occurred in an incorrect location — the once-per-revolution reference from the spindle-mounted sensor is arriving where it shouldn't. Fanuc routes the troubleshooting to alarm code 81 — the same fault on the motor sensor — with the checks re-aimed at the spindle-side hardware.
The AL-81 procedure, aimed at the spindle sensor
- Sensor parameters (B-65280EN) — first suspect after amplifier/parameter work.
- Sensor adjustment: the spindle-mounted αiCZ/BZ-type sensor's signal must be within spec — a gap disturbed during spindle bearing, belt or ring work shifts the reference. Adjust; if it cannot be brought into spec or is absent, replace cable and sensor together.
- Sensor ring integrity: a damaged tooth or a ring that has shifted on the spindle moves the reference physically — the classic aftermath of a crash or over-aggressive puller work.
- Shielding and routing: shield continuity, frame-ground via cable clamp, separation from power leads — noise injects phantom reference pulses (method per AL-41).
- The amplifier input — last.
Tip: The one-rotation-signal alarms map by sensor: position coder → AL-41; motor sensor → AL-81; spindle sensor → AL-85. Same physics, three mounting points. If AL-85 arrived with orientation drifting or Cs-contour parts going out of tolerance beforehand — that drift was this fault, pre-alarm.
Related guides
- Fanuc spindle alarm 81 (motor sensor Z position) — the full procedure
- Fanuc spindle alarm 84 (spindle sensor disconnected)
- Fanuc αi drive alarms — PSM, SVM & SPM codes
AL-85 after spindle work or a crash? JJ Automation inspects sensor rings, sets gaps, stocks spindle sensors and cables, and repairs amplifier inputs at component level. On-site service in NCR. WhatsApp us or call +91 88022 12394.