How much does it cost to fix Ariston error code 40-50 (ll-ll)?

Typical repair cost for the Ariston 40-50 (ll-ll) fault is £180-350 including labour.

40-50 (ll-ll) High

Ariston 40-50 (ll-ll) Fault Code

Q: What does the Ariston 40-50 (ll-ll) fault code mean?

Your boiler has detected that the internal fan responsible for safely exhausting fumes is not spinning or responding correctly, so it has shut down to keep you safe.

Also written as 4050LLLL — same fault.

The Ariston 40-50 (ll-ll) fault code means: your boiler has detected that the internal fan responsible for safely exhausting fumes is not spinning or responding correctly, so it has shut down to keep you safe.. It appears on 4 Ariston models in our database.

Technical description: Operating control fault of the fan

Typical repair cost £180-350 (including labour)

Engineer required

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

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Ariston models that show the 40-50 (ll-ll) fault code

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

Source

Ariston 40-50 (ll-ll) fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

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