BoilerFaultCodesPro Flow Thermistor Fault Code
Also written as FLOWTHERMISTOR — same fault.
The Pro Flow Thermistor fault code means: your boiler has detected a problem with the internal sensor that monitors the temperature of the water leaving the unit, causing it to stop for safety.. It appears on 1 Pro model in our database.
Technical description: Reset the appliance - if the boiler fails to operate then please contact Procombi (if under warranty) or alternatively a Gas Safe Registered Engineer if outside of the warranty period.
DIY fix possible
Locate the reset button or dial on the front control panelPress or turn to the 'Reset' position for five secondsWait for the boiler to restart; if the fault returns immediately, professional repair is required
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Pro models that show the Flow Thermistor fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Pro Flow Thermistor fault code information on this page is sourced and cross-checked against the official Pro service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026