BoilerFaultCodesYour boiler has switched itself off because it has reached an unsafe temperature and needs to cool down and be reset.
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 Overheat Lockout section of the fault finding instructions.
What causes this fault?
This fault occurs when the water inside the heat exchanger becomes too hot, triggering a safety sensor to shut the system down to prevent damage. The most common reasons are a failed pump that isn't moving water away quickly enough, or a build-up of debris like sludge that is blocking the internal pipework.
This issue often surfaces during the first cold spell of autumn when the heating is turned on after being dormant all summer, which can cause internal parts like the pump to seize.
DIY fix possible
Check that your radiator valves are open and not turned to zero.Ensure there is enough water pressure in the system by checking the external gauge.Turn the selector switch to the 'Reset' position for five seconds, then turn it back to 'On'.
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 Red LED: Flash, Green LED 1: Off, Green LED 2: On — no call-out fees, no surprises.
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Potterton Promax 15/2 HE Plus 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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