High
FAIL POINT I on Worcester Bosch Greenstar 25Si

Your boiler has detected a communication error with its internal sensors or electrical connections, causing it to stop operating as a safety precaution.

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

Sensor Fault: ST16 connector loose, DHW sensor resistance/continuity fault (yellow wires), CH sensor resistance/continuity fault (red wires), or gas valve solenoid resistance fault.

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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