CH1≠CH2 Pilz — Safety relay does not reset — cross-channel fault or contactor feedback
At a glance
- Severity
- FAULT STOP
- Domain
- SAFETY
- Reference standard
- IEC 62061 / ISO 13849-1
- Product / context
- Channel discrepancy error
What it means
The safety relay does not reset after the reset command. The diagnostic LEDs indicate an EDM feedback error or a discrepancy between the redundant channels. The machine remains in a safe state.
Probable causes
- EDM feedback contact of the external contactor not closed: contactor welded or coil faulty.
- Discrepancy between channel 1 and channel 2 (one input closed, the other open, discrepancy time exceeded).
- Safety contactor with welded NC auxiliary contact (feedback permanently closed).
- Incorrect wiring of the EDM (External Device Monitoring) feedback circuit.
Where to start
Observe the diagnostic LEDs on the safety relay. Does the LED indicate an EDM / feedback error or a cross-channel error?
Full guided diagnosis in the app
The diagnostic tree for this fault has 7 guided steps with measurements, checks and resolutions. You'll find it in ElectraIQ, one of the four IndexOS apps: free, works offline.
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