F6 High

Saunier Duval F6 Fault Code

The Saunier Duval F6 fault code means: your boiler has detected a problem with the sensor that monitors the temperature of the water heading to your radiators, causing the system to shut down for safety.. It appears on 6 Saunier Duval models in our database.

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 thermistor fault. Thermistor cable defective/broken. Thermistor faulty. Check that thermistor attached correctly to pipe

What causes the Saunier Duval F6 fault?

This fault occurs when the boiler's internal computer stops receiving a reliable signal from the sensor that monitors the temperature of the water leaving the unit. The most common reason is that the sensor has physically failed due to age, or the electrical connection between the sensor and the main control board has become loose or damaged.

Typical repair cost £100-£180 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Saunier Duval models that show the F6 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Saunier Duval F6 fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026