BoilerFaultCodesYour boiler has likely overheated, causing it to shut down and run the fan at full speed as a safety measure to cool the internal components.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Go to section 'J' (Overheat thermostat operated or faulty).
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit, triggering a safety shut-off to prevent damage. The most common reasons are a failure of the internal pump to move water away from the burner or a blockage within the main heat exchanger that restricts flow.
This issue is more frequent in autumn or winter when the heating is first turned on after a long summer break, often because the pump has seized due to inactivity.
DIY fix possible
Ensure all radiator valves are open and there is no air trapped in the systemAllow the boiler to cool down for at least 20 minutesTurn the selector switch to the reset position and hold for 5 seconds, then release
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Fan runs at max speed neon flashing — no call-out fees, no surprises.
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Potterton Performa System HE is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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