Medium Warning
A7 on Worcester Bosch Greenstar i

Your boiler is struggling to accurately measure the temperature of your hot water, which usually means it cannot provide a consistent supply to your taps.

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

Tank sensor fault: Tank sensor (8000 - 20000 ohms at room temperature), Wiring and connections to sensor.

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring your tap water temperature fails or begins sending incorrect electrical signals to the main control board. The most common reason is that the sensor has suffered from wear and tear or internal corrosion over time, preventing it from accurately telling the boiler how hot the water is. In some cases, the error can also be caused by loose or damaged wiring connecting the sensor to the boiler's computer.

Engineer required

This fault requires 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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