High
EE3333 on Ariston Clas One

Your boiler is failing to start because it detects a faulty signal from its internal airflow sensor before the ignition process has even begun.

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 closed before the ignition sequence has begun

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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