BoilerFaultCodesYour boiler is struggling to detect a flame or control the gas flow properly, which means it cannot heat your home reliably.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flame sensing or gas valve modulation fault (Section G or I)
What causes this fault?
This fault occurs when the boiler's internal computer loses track of the flame or cannot adjust the gas pressure to the correct level. The most common reason is a dirty or worn-out sensor that can no longer 'see' the fire, or a mechanical failure within the gas valve preventing it from opening properly.
This issue often surfaces during the first cold snap of autumn when the gas valve is forced to work harder after sitting idle throughout the summer.
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.
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A boiler cover plan would cover faults like Burner output modulates neon flashing — no call-out fees, no surprises.
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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.
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