BoilerFaultCodesYour boiler is unable to control the flow of gas required for ignition, meaning it cannot light to provide heat or hot water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Stepper motor fault (gas valve)
What causes this fault?
This fault occurs when the boiler's internal computer is unable to communicate with or move the motor that controls the gas supply. The most common reason is that the motor has physically jammed or its electronic windings have burnt out, preventing the valve from opening to let fuel in for ignition.
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 15 — no call-out fees, no surprises.
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Glow-worm 18si 24ci 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.
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