A Siemens 810 GA3 control on a 1996 Magerle surface grinder lost its stored parameters after remaining without batteries for several years. After fitting new batteries and transferring the available backup, the control accepted TEA1, TEA2, SEA, RPA1, RPA2, RPA3, and TOA, but displayed German axis labels and soft keys, PLC STOP, alarm 3040 “Fields/var. not displayable,” and “NO KEY-OPERATED SWITCH” when opening NC MD.
Establish the Post-Restore Fault Baseline
| Observed condition | Evidence-supported interpretation | Required check |
|---|---|---|
| German labels and soft keys | The restored data may not include the English HMI text set. | Confirm whether the backup contains language or text data beyond the transferred files. |
| NO KEY-OPERATED SWITCH | Machine-data access may require the physical key-operated switch in Service mode. | Verify the switch position and its input state before changing NC machine data. |
| PLC STOP and 3040 Fields/var. not displayable | An incomplete PLC restoration or a version mismatch is suspected, but the evidence does not distinguish between them. | Audit backup completeness and compare the restored software/data versions with the control. |
Restore Access to NC Machine Data
Place the hardware key-operated switch in Service mode, then retry the NC MD soft key. If the message remains, verify that the control detects the switch state; changing the mechanical position alone does not prove that the corresponding input or authorization reached the control.
The report associates machine data 199 or 250 with language selection, but it does not establish which value applies to this machine or what value to enter. Do not alter either setting until NC MD access is restored and the machine-specific backup or documentation identifies the correct setting.
Separate Language Data from the PLC Fault
The return to German does not by itself prove that the PLC program is defective. It indicates that the English HMI text was either absent from the backup, omitted from the transfer, or not activated. Inventory the backup for language-specific HMI files and compare it with the files actually loaded before changing machine data.
Do not treat a language-setting change as a remedy for PLC STOP or alarm 3040. Verify the HMI language and PLC restoration as separate workstreams, then confirm each result independently.
Audit the PLC Restore Sequence and Missing Files
The available procedure reportedly places PCP and PCA after TEA1 and TEA2, but those files are absent from the backup. The evidence does not define their contents, so substituting files from another machine would introduce unknown machine-specific data and is not a controlled recovery method.
- Preserve the current backup and record every available file: TEA1, TEA2, SEA, RPA1, RPA2, RPA3, and TOA.
- Confirm that PCP and PCA are genuinely absent rather than stored under another backup set or location.
- Compare the backup inventory and loading order with the applicable Siemens reload procedure for this exact control configuration.
- Check whether the restored PLC and control data versions match the installed control before attributing alarm 3040 solely to missing files.
- After correcting an identified omission or mismatch, verify that PLC STOP clears, alarm 3040 no longer appears, NC MD opens with the authorized key-switch state, and the intended language texts display.
FAQ
Why does a Siemens 810 GA3 show NO KEY-OPERATED SWITCH?
NC machine-data editing may require the physical key-operated switch in Service mode. Set the switch accordingly and verify that the control detects its state before attempting NC MD access again.
What causes PLC STOP with Siemens alarm 3040 Fields/var. not displayable?
The available evidence points to an incomplete PLC load or a version mismatch as hypotheses. Audit the backup contents, restore sequence, and installed data versions before selecting a corrective action.
Can PCP and PCA files from another machine replace missing backup files?
Do not substitute them without verified compatibility. Their contents are not established by the available evidence, and files from another machine may contain configuration-specific data.