High Lockout
F43 on Glow-worm Ultracom hxi

Your boiler has lost its memory of whether it is a 24kW or 30kW model, meaning it cannot operate safely until its settings are re-programmed.

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

Boiler configuration fault (refer to 24 or 30 kw)

What causes this fault?

This fault occurs when the boiler's main control board loses the specific software settings that tell it which model it is currently operating. This is usually caused by a sudden electrical surge or a technical malfunction within the Printed Circuit Board's memory chip. Without this identity information, the boiler shuts down as a safety precaution because it doesn't know how much gas to burn.

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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Related fault codes

F70View →F61View →F62View →

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