BoilerFaultCodesYour boiler thinks it is being told to heat your home even though your thermostat is turned off, usually due to a wiring fault or a stuck control part.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Boiler operating without live demand at ST10-LR (from external roomstat timer)
What causes this fault?
This fault occurs when the boiler detects an electrical signal telling it to provide heating, even though your thermostat or programmer is switched off. It is usually caused by a 'stuck' mechanical switch inside an external control or a wiring error that is back-feeding electricity to the boiler. Because the boiler cannot safely stop the heating cycle when requested, it shuts down as a safety precaution.
This issue often comes to light during the first cold spell of autumn when homeowners first switch their heating systems back on after a long summer break.
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 Blue light: On, Lockout reset: Off (Alt 1) — no call-out fees, no surprises.
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