How much does it cost to fix Atag error code C1 51?

Typical repair cost for the Atag C1 51 fault is £200-350 including labour.

C1 51 High

Atag C1 51 Fault Code

Q: What does the Atag C1 51 fault code mean?

Your boiler has detected that the internal fan responsible for safety and combustion is not spinning at the correct speed, so it has shut down to prevent any risk.

Also written as C151 — same fault.

The Atag C1 51 fault code means: your boiler has detected that the internal fan responsible for safety and combustion is not spinning at the correct speed, so it has shut down to prevent any risk.. It appears on 4 Atag models in our database.

Technical description: Fan error (speed control is not achieved or is outside of range)

Typical repair cost £200-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Atag models that show the C1 51 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Atag C1 51 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026