High
H9 on Worcester Bosch Highflow 250

Your boiler is struggling to accurately measure the temperature of the water inside its internal storage tank, which means it cannot reliably provide hot water.

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

Tank sensor 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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Related fault codes

H7View →H8View →

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