High
F4 on Ideal Mexico

Your boiler has lost its ability to measure the temperature of the water leaving the unit, meaning it cannot operate safely and has shut itself down.

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

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

F3View →F5View →L2View →

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