How much does it cost to fix Potterton error code On On Flash?

Typical repair cost for the Potterton On On Flash fault is £250-400 including labour.

On On Flash High

Potterton On On Flash Fault Code

Q: What does the Potterton On On Flash fault code mean?

Your boiler's internal electronic brain has detected a critical error and is unable to safely control the heating system, meaning the boiler has shut down.

Also written as ONONFLASH — same fault.

The Potterton On On Flash fault code means: your boiler's internal electronic brain has detected a critical error and is unable to safely control the heating system, meaning the boiler has shut down.. It appears on 4 Potterton models in our database.

Technical description: PCB Fault - Replace PCB.

Typical repair cost £250-400 (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 On On Flash fault code

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

Source

Potterton On On Flash 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