Fanuc alarm 04: Open phase in converter main-circuit input (PSM alarm mirrored)
αi SPM · Fanuc αi SPM
What it means
When displayed on the αi SPM status display this code indicates that the three-phase input to the main circuit of the upstream PSM has lost a phase. The fault is in the common power supply, not in the SPM itself — always read the PSM's own 7-segment display.
Likely causes
- Lost phase in incoming 3-phase supply
- Faulty input contactor, fuse or wiring to the PSM
- PSM detection circuit failure
Triage note: Mirrored PSM alarm codes on SPM: 4, 11, 30, 33, 51, 57, 58, b1, b2, b3.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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A06B-6110-Hxxx / A06B-6120-Hxxx (PSM, only if supply checks pass)
power-supply · Check if others ruled out
Need the part urgently?
Send us alarm 04 with your machine details — typical RFQ turnaround is 24–48h.