High
A5 on Worcester Bosch Greenstar 25 HE Combi

Your boiler is struggling to accurately measure the temperature of the water inside the storage tank, which is preventing your hot water from heating up correctly.

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 NTC 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

A8View →B1View →E9View →

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