High Lockout
A55 on Ferroli BlueHelix Pro 25C

Your boiler's internal computer has encountered a critical electronic failure and can no longer control the heating or hot water safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Printed circuit board (PCB) AGC01 fault

What causes this fault?

This fault occurs when the boiler's main control board suffers a hardware malfunction or a breakdown in electronic communication. The most common reason is a component failure on the circuitry itself or an electrical short caused by wear and tear or moisture ingress over time.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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