How much does it cost to fix Saunier Duval error code Red light F ON?

Typical repair cost for the Saunier Duval Red light F ON fault is £120-250 including labour.

Red light F ON High

Saunier Duval Red light F ON Fault Code

Q: What does the Saunier Duval Red light F ON fault code mean?

Your boiler has detected a safety issue and has automatically switched itself off to prevent damage or dangerous operation.

Also written as REDLIGHTFON — same fault.

The Saunier Duval Red light F ON fault code means: your boiler has detected a safety issue and has automatically switched itself off to prevent damage or dangerous operation.. It appears on 1 Saunier Duval model in our database.

Technical description: Boiler will not work. Depress the boiler safety cutoff reset button G

Typical repair cost £120-250 (including labour)

DIY fix possible

Locate the reset button labeled 'G' on the front control panel.Press and hold the button firmly for a few seconds to see if the boiler restarts.If the boiler fires up, monitor it for a few hours to ensure the light does not return.

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Saunier Duval models that show the Red light F ON fault code

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

SD 30e Repair: £120-250

Source

Saunier Duval Red light F ON 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