Medium Warning
A7 on Worcester Bosch Greenstar 25HE

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

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

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

Hot water NTC sensor defective.

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring your tap water temperature fails or sends an incorrect signal to the boiler's control board. The most common reason is that the sensor has experienced electrical fatigue over time or has developed a loose connection, preventing the boiler from knowing how much to heat the water. In some cases, a build-up of limescale on the sensor can also insulate it, leading to inaccurate readings and this error code.

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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