BoilerFaultCodesYour boiler thinks a flame is present even though it hasn't turned the gas on, usually caused by a blocked drain or a faulty sensor.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flame detected with closed gas valve. Check ionization probe/cable. Check condensate outlet not blocked & vent tube clear
What causes this fault?
This fault occurs when the boiler's control system senses a flame internal to the unit even though it hasn't signaled the gas valve to open. The most common cause is a surge of water or moisture backing up into the combustion chamber due to a blockage in the condensate drain or a buildup of carbon on the sensing probe. In some cases, a damaged ignition lead or a failing control board can also send a false electrical signal that mimics the presence of a flame.
This fault is more common during the winter months, as freezing temperatures can cause the external condensate pipe to block with ice, forcing water back into the boiler.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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