Neon D illuminated Low

Alpha Neon D illuminated Fault Code

Also written as NEONDILLUMINATED — same fault.

The Alpha Neon D illuminated fault code means: your boiler is receiving power correctly and is currently in its normal standby state.. It appears on 1 Alpha model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Mains supply on

DIY fix possible

No action is required as this is a status indicator rather than a fault code.If you have no heating or hot water, ensure your external thermostat or programmer is set to demand heat.

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Alpha models that show the Neon D illuminated fault code

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

Source

Alpha Neon D illuminated fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026