BoilerFaultCodesTechnical description
Indicates that the flue or flue terminal is blocked or obstructed in some way, or that there is an internal fault.
What causes this fault?
This fault occurs when the boiler's safety sensors detect that harmful exhaust gases are not being cleared from the system effectively. The most common reasons are a buildup of debris in the fan or air tubes, or a mechanical failure in the switch that confirms the fan is spinning fast enough to operate safely.
This issue is frequently seen during periods of high winds, which can create back-pressure in the flue, or in autumn when falling leaves can physically block the external terminal.
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.
Find a Gas Safe engineer
Search the official register →