BoilerFaultCodesPotterton Flow Thermistor Fault Fault Code
Also written as FLOWTHERMISTORFAULT — same fault.
The Potterton Flow Thermistor Fault fault code means: your boiler has switched itself off because the internal temperature sensors are giving conflicting or unusual readings, meaning it cannot safely regulate the heat.. It appears on 2 Potterton models in our database.
Technical description: Lockout Burner Mains - Automatic Flow Thermistor Fault (Thermistors reading outside of limits or difference between readings outside of limits)
What causes the Potterton Flow Thermistor Fault fault?
This fault occurs when the sensors responsible for monitoring the temperature of the water leaving the boiler fail to report consistent data. The most common reason is that the internal components of the sensor have degraded over time, though it can also be caused by loose wiring or a communication error within the main control board.
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 Flow Thermistor Fault fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton Flow Thermistor Fault 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