BoilerFaultCodesYour boiler's internal computer has suffered a technical failure and can no longer control the heating process safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Internal failure - electronic
What causes this fault?
This fault occurs when the boiler's main control board suffers an internal electrical failure or memory error, preventing it from processing instructions. The most common reason is age-related wear on the electronic components or a power surge that has damaged the delicate circuitry inside the unit.
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 405 — no call-out fees, no surprises.
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