Preheat neon flashing Low

Potterton Preheat neon flashing Fault Code

Also written as PREHEATNEONFLASHING — same fault.

The Potterton Preheat neon flashing fault code means: your boiler is letting you know that the hot water preheat function is active because the control dial is turned up.. It appears on 1 Potterton 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: Preheating function starts after 25 seconds. Preheat control is not at minimum position. Go to section ‘L’.

What causes the Potterton Preheat neon flashing fault?

This is not a mechanical failure but a status indicator caused by the position of the hot water temperature dial. When this dial is moved away from the minimum setting, the boiler automatically warms up the internal heat exchanger so that hot water reaches your taps faster. The flashing light simply confirms that the boiler is currently performing this background task.

This function may be more noticeable in winter when incoming mains water is much colder, as the boiler will need to fire more frequently to maintain the preheat temperature.

DIY fix possible

Locate the preheat control knob on the front panel.Turn the dial fully anti-clockwise to the minimum position if you wish to disable this feature.Observe if the flashing neon light stops once the dial is at minimum.

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Potterton models that show the Preheat neon flashing fault code

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

Source

Potterton Preheat neon flashing fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026