High Lockout
F0 on Worcester Bosch Greenstar 25HE

Your boiler's computer brain has suffered a serious internal glitch and is unable to communicate with its own sensors or controls.

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

Internal error.

What causes this fault?

This fault occurs when the boiler’s main control board experiences a total communication failure between its internal components. It is often caused by an electrical surge, a moisture-related short circuit, or simply the natural degradation of the aging electronics inside the unit. Because the 'brain' can no longer process safety data, the boiler shuts down entirely to prevent any unsafe operation.

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

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