High Lockout
4.8 on Ideal Logic Max Heat

Your boiler has lost its ability to measure the temperature of the water leaving the unit, meaning it cannot safely regulate the heat.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Flow Thermistor Fault

What causes this fault?

This fault occurs when the internal sensor responsible for tracking the temperature of the water leaving your boiler has failed or is sending garbled data. The most common reason is that the sensor's electrical resistance has drifted out of range due to age, or a loose connection in the wiring is preventing the control board from receiving a steady signal.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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