BoilerFaultCodesYour boiler has encountered an internal electronics failure that is preventing it from starting up correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Internal error. Transformer. All connections to control board. Otherwise replace control board.
What causes this fault?
This fault occurs when the boiler's internal computer system suffers a critical communication breakdown. It is typically caused by a failure in the power transformer or a physical defect on the main control board that prevents electricity from reaching the vital components safely. Without this internal power supply, the boiler cannot perform its safety checks and will refuse to fire up.
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 H1 — no call-out fees, no surprises.
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