BoilerFaultCodesYour boiler's internal computer has developed a fault and can no longer communicate with the main control 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 or the heat control module HCM) is defective- the HCM and control box connections need to be checked
What causes this fault?
This fault occurs when the boiler's internal processor fails to read the data chip that tells it how to operate safely. The most common reason is an electronic failure within the Heat Control Module or the main circuit board, effectively leaving the boiler without its 'memory' or operating instructions.
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 B7257 — no call-out fees, no surprises.
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