BoilerFaultCodesYour boiler's main internal computer has likely developed an electrical fault and can no longer control the system safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Controller DBM23B error – controller could have an internal error
What causes this fault?
This fault occurs when the boiler's central control board suffers a hardware failure, meaning it can no longer process data or send signals to other components. The most common reason is electrical degradation of the circuitry over time or a sudden power surge that damages the sensitive microprocessors.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like F51 — no call-out fees, no surprises.
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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.
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