High Lockout
FAIL POINT C on Worcester Bosch Greenstar Si

Your boiler’s internal control system has suffered an electrical component failure and can no longer manage the heating process.

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

Green diode is damaged. Control board requires replacement.

What causes this fault?

This fault occurs when an electrical component on the boiler's internal computer, specifically a diode, burns out or degrades over time. Without this component functioning, the control board can no longer safely manage the signals required to fire the boiler, leading to a total system failure. It is typically caused by general wear and tear of the circuitry or a minor power surge that the board could no longer handle.

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

FAIL POINT DView →FAIL POINT EView →

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