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 safety sensors detect that air cannot flow freely into the unit or exhaust gases cannot exit through the flue pipe. The most common reasons are a physical blockage in the external pipework, such as debris or a bird's nest, or a mechanical failure of the fan which is responsible for pushing these gases out.
This fault is more common during the autumn and winter months, as fallen leaves or heavy snow can physically obstruct the external flue 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.
Avoid the next call-out bill
A cover plan would handle faults like F018: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.