BoilerFaultCodesYour boiler is still detecting a flame even after it has tried to shut off the gas, which is a safety conflict that requires a professional inspection.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing
What causes this fault?
This fault occurs when the boiler's internal sensors continue to detect a flame even after the gas supply should have been cut off. The most common reason is a gas valve that has become stuck open or a faulty electrode that is incorrectly reporting a flame to the control board. Because the boiler cannot guarantee it can stop the flow of fuel, it shuts down immediately as a critical safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 306 V — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.