High
2963 B on Worcester Bosch Greenstar 4000

Your boiler has stopped working because it is unable to accurately read the temperature of the water inside the unit.

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

The heat exchanger sensor or both supply and heat exchanger sensors are defect

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

2965View →2966View →

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