BoilerFaultCodesYour boiler's internal computer has encountered a critical error and cannot safely operate the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Control box errors – possible faulty control box
What causes this fault?
This fault occurs when the boiler's internal computer brain fails to communicate correctly with the safety sensors and ignition components. It is physically caused by a microchip failure or a corrupted circuit on the main control board, preventing the boiler from managing the heating process safely. The most common reason is general electronic wear and tear or a power surge that has damaged the delicate internal wiring.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E25 — no call-out fees, no surprises.
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Keston C36 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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