BoilerFaultCodesYour boiler's main internal computer has developed a technical fault 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: Controller ABM03B error – controller internal error
What causes this fault?
This fault occurs when the boiler's internal computer chips suffer a hardware failure or a memory corruption, meaning the board can no longer process safety data correctly. The most common reason is electrical degradation of the circuitry over time or a sudden power surge that damages the sensitive components on the PCB.
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 F66 — no call-out fees, no surprises.
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