BoilerFaultCodesFerroli A04 Fault Code
The Ferroli A04 fault code means: your boiler has shut down because it detected a repeat issue with its exhaust system three times in one day.. It appears on 8 Ferroli models in our database.
Technical description: Flue gas fault – fault F07 happened 3 times in the last 24 hours
What causes the Ferroli A04 fault?
This fault occurs when the boiler's safety sensors detect that exhaust fumes are not being cleared away correctly through the flue pipe. It is triggered after the system identifies a recurring airflow issue several times in a single day, causing the boiler to shut down for safety. Common reasons include a failing fan, a blocked flue, or a faulty pressure switch that can no longer accurately monitor the flow of gases.
This issue can be more frequent during periods of heavy wind, as strong gusts can sometimes obstruct the flue terminal and interfere with the pressure readings.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ferroli models that show the A04 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ferroli A04 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 27 April 2026