High Lockout
F04 on Ideal Logic Max Combi

Your boiler has detected an issue with the sensor that monitors the temperature of the water leaving the unit, which means it cannot heat your home or water safely.

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 boiler's control board loses communication with the sensor that monitors the heat of the water leaving the unit. It is usually caused by the internal components of the sensor failing over time or a loose connection in the electrical wiring that links the sensor to the main computer.

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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Related fault codes

F1View →L2View →F3View →

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