Neon 4 lit (NO) High

Saunier Duval Neon 4 lit (NO) Fault Code

Also written as NEON4LITNO — same fault.

The Saunier Duval Neon 4 lit (NO) fault code means: your boiler has detected an internal communication failure and needs a professional electrical check to restore heating and hot water.. It appears on 2 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: Isolate supply, test harness continuity. If satisfactory replace printed circuit board.
Typical repair cost £200-400 (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 Neon 4 lit (NO) fault code

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

Source

Saunier Duval Neon 4 lit (NO) 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