What causes Beckhoff TwinCAT 3 (XAR/XAE) with EtherCAT fault ADS 1808?

1. Symbol path spelled differently from the PLC (program, GVL or namespace prefix missing): Compare the full path (e.g. MAIN.nCounter, GVL_IO.bStart) with the symbols of the running project. 2. Variable not in the symbol file of the running project: Check the project running on the target is the one with the variable and that symbol creation includes it. 3. Client connected to the wrong PLC runtime port: Check the AMS port (851, 852…) matches the PLC project that owns the variable.

TwinCAT ADS Error 1808 (0x710) Symbol Not Found: Fix

Beckhoff: symbol not found. The client asked for a handle or value by symbol name and the PLC runtime on that port has no symbol with that name.

Diagnose this with AI

Upload a keypad photo, the fault history or a parameter export from your Beckhoff TwinCAT 3 (XAR/XAE) with EtherCAT. InduQT compares the evidence and suggests the next useful checks.

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When it happens

When an HMI, SCADA or OPC UA/ADS client creates handles
After a PLC download that renamed or removed variables

Likely causes and checks

1Symbol path spelled differently from the PLC (program, GVL or namespace prefix missing)

Points to it: Only the new or edited tags fail; others on the same port work.
Check: Compare the full path (e.g. MAIN.nCounter, GVL_IO.bStart) with the symbols of the running project.

2Variable not in the symbol file of the running project

Points to it: Variable exists in the source but was not downloaded, or symbol generation excludes it.
Check: Check the project running on the target is the one with the variable and that symbol creation includes it.

3Client connected to the wrong PLC runtime port

Points to it: All symbols fail on this connection.
Check: Check the AMS port (851, 852…) matches the PLC project that owns the variable.

Telling it apart

ADS 1808 means the name was not found; ADS 1809 (0x711) means the symbol exists but the handle is stale after an online change.
ADS 6 on the same port means no PLC is running at all.

Evidence to collect

Exact symbol name used by the client
Symbol list of the running PLC project
Client port and target NetId
Date of the last download or online change

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Beckhoff TwinCAT 3 (XAR/XAE) with EtherCAT fault ADS 1808: Symbol not found (0x710, ADSERR_DEVICE_SYMBOLNOTFOUND)