Medium Warning
1-b4 on Worcester Bosch Greenstar 8000 Life/Style

Your boiler is struggling to accurately measure the temperature of the water going to your taps, which might result in the water being too hot or too cold.

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 temperature outlet: Hot water temperature.

What causes this fault?

This fault occurs when the boiler's internal computer receives an unconventional or missing signal from the sensor that monitors your tap water temperature. The most common reason is that the sensor has either developed a physical fault or has been affected by a small amount of corrosion on its electrical connections. In some cases, localized limescale buildup around the sensor can also cause it to send inaccurate readings.

Engineer required

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

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Related fault codes

1-b2View →1-b3View →

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