BoilerFaultCodesWorcester Bosch 1025 Fault Code
The Worcester Bosch 1025 fault code means: your boiler's internal thermometer that measures the water returning from your radiators has developed a fault and can no longer read the temperature correctly.. It appears on 8 Worcester Bosch models in our database.
Technical description: Return temp. sensor is faulty
What causes the Worcester Bosch 1025 fault?
This fault occurs when the sensor responsible for measuring the water coming back from your radiators fails to send a reliable signal to the boiler's control board. The most common reason is that the internal electrical components of the sensor have worn out or corroded over time, or a wire has become loose or damaged. Because the boiler can no longer verify the water temperature, it shuts down as a safety precaution to prevent overheating.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the 1025 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 1025 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026