On Flash Flash High

Potterton On Flash Flash Fault Code

Also written as ONFLASHFLASH — same fault.

The Potterton On Flash Flash fault code means: your boiler has detected that it is running without enough water inside, which means it cannot safely heat your home and has shut itself down to prevent damage.. It appears on 4 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: Dry-Fire - go to Dry-Fire section of the fault finding instructions.
Typical repair cost £90-180 (including labour)

DIY fix possible

Check your boiler pressure gauge; if it is below 1 bar, you need to repressurise the system.Locate the filling loop (usually a silver braided hose with one or two valves) connected to the boiler pipes.Slowly open the valve(s) to allow water to enter until the gauge needle reaches between 1 and 1.5 bar, then turn the valve(s) firmly off.

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Potterton models that show the On Flash Flash fault code

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

Source

Potterton On Flash 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