Mains ON Only High

Potterton Mains ON Only Fault Code

Also written as MAINSONONLY — same fault.

The Potterton Mains ON Only fault code means: your boiler has stopped working and is showing a fault light, meaning it has detected an internal error that has forced it to shut down for safety.. It appears on 5 Potterton 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: Green LED: OFF, Red LED: ON
Typical repair cost £150-300 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Potterton models that show the Mains ON Only fault code

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

Source

Potterton Mains ON Only 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