A 0 3 Emergency

Ferroli A 0 3 Fault Code

Also written as A03 — same fault.

The Ferroli A 0 3 fault code means: your boiler has detected that waste gases are not being cleared away safely and has automatically shut down to prevent a build-up of fumes.. It appears on 1 Ferroli model in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Flue safety device intervention: Flue partially blocked or insufficient
Typical repair cost £120-250 (including labour)

Engineer required

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

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Ferroli models that show the A 0 3 fault code

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

Source

Ferroli A 0 3 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026