BoilerFaultCodesWhat the manual says
Manufacturer manualFlue and/or air supply duct is blocked.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that air cannot flow freely through the system to support safe combustion. It is usually caused by an external obstruction in the flue pipe, a buildup of debris, or a mechanical failure in the fan that pushes the exhaust gases out of your home.
This fault is more common during autumn and winter, as falling leaves or nesting birds can block the external flue terminal, and heavy snow can obstruct the air intake.
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.
Avoid the next call-out bill
A cover plan would handle faults like F018: no call-out fees, no surprise bills.
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