BoilerFaultCodesYour boiler has detected a problem with how it disposes of waste gases, often caused by a blockage or a fault in the air flow system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Air pressure switch contact error – wrong flue baffle obstructed or not correctly sized
What causes this fault?
This fault occurs when the boiler's internal sensor detects that harmful exhaust gases are not being cleared away safely or that the fresh air supply is restricted. The most common reasons are a buildup of debris in the flue pipes, a failing fan that cannot push air through the system, or a pinched silicone tube leading to the pressure sensor.
This fault is more common during periods of high winds, as strong gusts can interfere with the air pressure balance within the flue system and trigger a safety shutdown.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like F05 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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