Medium
H12 on Worcester Bosch Greenstar 12i System

Your boiler is struggling to detect the temperature of your hot water cylinder, which means it may fail to heat your water properly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Storage sensor cylinder sensor.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

H08View →

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