BoilerFaultCodesYour boiler's internal computer has developed a critical error and can no longer control the heating 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: Main PCB fault
What causes this fault?
This fault occurs when the boiler's internal control board suffers a hardware failure and can no longer process data correctly. The most common reason is damage to the electrical components on the board, often caused by natural wear and tear over time or an accidental electrical surge.
This fault is slightly more common during the winter months when the boiler is under constant heavy use, which can lead to overheating or failure of older electrical components.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 0A21 — 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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