High
F19 on Saunier Duval Isofast

Your boiler has lost its connection to the sensor that monitors the flow of water, meaning it cannot confirm that water is circulating properly through your heating system.

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

Central heating flow sensor unclipped

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

F20View →F22View →

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