BoilerFaultCodesPotterton 25 Fault Code
The Potterton 25 fault code means: your boiler has detected that a temperature sensor is not working correctly, which has caused the system to stop running to prevent overheating.. It appears on 5 Potterton models in our database.
Technical description: Fault on Central Heating Sensor
What causes the Potterton 25 fault?
This fault occurs when the boiler's control board can no longer read accurate information from the flow temperature sensor. The most common reason is that the internal thermistor has physically failed or developed a short circuit, meaning the boiler can no longer safely monitor how hot the water is getting. In some cases, it may also be caused by loose or damaged wiring connecting the sensor to the main control unit.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Potterton models that show the 25 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton 25 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026