Mains On (Green Light) Low

Potterton Mains On (Green Light) Fault Code

Also written as MAINSONGREENLIGHT — same fault.

The Potterton Mains On (Green Light) fault code means: your boiler is receiving electrical power and is ready to operate as normal.. 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: This indicates that there is electricity to the Boiler.

What causes the Potterton Mains On (Green Light) fault?

This is not a fault but a status indicator showing that the boiler is successfully connected to the mains electricity supply. It confirms that the internal control board is receiving power and the unit is in standby mode, ready to fire up when you turn on your heating or hot water. If the light is on but the boiler isn't heating, the issue likely lies with your external thermostat or a specific internal component rather than the power supply itself.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Potterton models that show the Mains On (Green Light) fault code

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

Source

Potterton Mains On (Green Light) 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