Medium
A7 on Worcester Bosch Greenstar Utility 18/25

Your boiler is experiencing a communication problem with its internal temperature sensor, causing it to shut down unexpectedly from time to time.

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.

What the manual says

Manufacturer manual

Intermittent lock-out

From this model's manual
Verified against the Worcester Bosch Greenstar Utility 18 25 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the boiler's main control board loses its connection with the temperature sensor that monitors the heat exchanger. The most common reason is that the sensor has developed an internal electrical failure or the wiring connecting it to the circuit board has become loose or corroded over time.

Engineer required

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

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