High
F4 on Ferroli Tempra 12 18

Your boiler has detected an issue with its internal ventilation, meaning it cannot safely remove combustion gases, so it has shut down to prevent potential danger.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

The air pressure switch is not making contact (contacts open). Check the fan, the venturi, the pressure switch and the flue.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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