BoilerFaultCodesSaunier Duval F1, F4 Fault Code
Also written as F1F4 — same fault.
The Saunier Duval F1, F4 fault code means: your boiler is failing to start because it cannot get the fuel it needs to produce a flame, meaning you currently have no heating or hot water.. It appears on 2 Saunier Duval models in our database.
Technical description: Ignition fault, boiler fialed to light. No gas / Insufficient gas. Incorrect gas valve adjustment. Electrode ignition lead defect. Electrnic igniter defective. Check air inlet duct and connections to igniter unit
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Saunier Duval models that show the F1, F4 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Saunier Duval F1, F4 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