High
b3 on Worcester Bosch Greenstar 25 HE Combi

Your boiler is struggling because it has detected an issue with the electrical board that controls its internal communications.

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

Data error Replace control board.

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

b1View →b2View →b4View →

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