BoilerFaultCodesYour boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheat thermostat operated. Go to section ‘J’.
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to cut power to the burner. The most common reasons are a failed pump that isn't moving water around the system or a blockage in the main heat exchanger caused by a buildup of sludge and debris. It can also happen if the system has become air-locked, preventing the heat from being carried away from the appliance.
This fault is frequently seen at the start of autumn when the heating is turned on for the first time after summer, as pump components can seize up during long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully openEnsure the system water pressure is between 1.0 and 1.5 barTurn the selector switch to the reset position for five seconds and then back to the heating/hot water mode
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 70 neon flashing — no call-out fees, no surprises.
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Potterton Performa 28i 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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