Siemens alarm 25000: Axis %1 hardware fault of active encoder
SINUMERIK axis alarm (encoder hardware) · Siemens 840D/810D powerline
What it means
Encoder signals missing, out of phase or shorted - active position feedback declared unusable.
Likely causes
- encoder failure (crash damage, bearing wear, contamination)
- measuring-system cable short/open, esp. in drag chains
- DRIVE-CLiQ chain instability (on sl) or connector corrosion
- coolant in encoder connector
Triage note: Clears only with POWER ON; re-reference axis afterwards.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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6FX5002-… / 6SL3066-0BA00-…
measuring/DRIVE-CLiQ cable · Primary suspect
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encoder per axis (EnDat absolute / glass scale)
encoder or linear scale · Primary suspect
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6SL3055-0AA00-… (SMC20/SME)
DRIVE-CLiQ sensor evaluation module (840D sl) · Common cause
Need the part urgently?
Send us alarm 25000 with your machine details — typical RFQ turnaround is 24–48h.