What does the Saunier Duval Neon 3 NOT lit fault code mean?

Your boiler is failing to clear combustion gases properly, so it has safely shut itself down to prevent any risk.

How much does it cost to fix Saunier Duval error code Neon 3 NOT lit?

Typical repair cost for the Saunier Duval Neon 3 NOT lit fault is £150-300 including labour.

Air flow proving fault - that is fan or air pressure switch

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Six most common causes of dropping pressure.

Each noise points to a different fault.

Safety-critical — turn off, read this.