Fanuc alarm SP9031: MOTOR LOCK OR V-SIG LOST
spindle alarm (serial spindle, alpha i) · Fanuc 0i-D
What it means
The commanded motor did not rotate at the commanded speed: either the shaft is physically locked, or the V-phase speed detection signal disappeared. The amplifier distinguishes stall from feedback loss using the estimated-speed observer.
Likely causes
- Mechanically locked spindle (brake engaged, seized gearbox/bearings)
- Loss of one channel of speed feedback
- Motor power cable with a broken phase conductor
Triage note: Rotate the spindle by hand with drives disabled to separate mechanical vs electrical causes.
Need the part urgently?
Send us alarm SP9031 with your machine details — typical RFQ turnaround is 24–48h.