BoilerFaultCodesYour boiler thinks it sees a flame even though it should be turned off, which prevents it from starting up safely.
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 even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear.
What causes this fault?
This fault occurs when the boiler's control system detects an electrical current that signals a flame is present, even though the gas should be turned off. This is often caused by moisture on the internal sensors or a failing circuit board that is misinterpreting signals. Essentially, the boiler enters a safety mode because it cannot guarantee it is safe to ignite the gas.
This issue can occasionally follow heavy wind or rain, as moisture driven into the flue can dampen the internal electrodes and trigger a false reading.
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 F7 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch CDi Classic is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.