BoilerFaultCodesYour boiler has sensed that parts of the internal system have become too hot, causing it to shut down automatically 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: Overtemperature protection intervention
What causes this fault?
This fault occurs when the internal temperature of the boiler rises above a safe limit, usually because water isn't moving through the system fast enough to carry heat away. The most common reasons are a failing circulation pump, a build-up of sludge or limescale blocking the heat exchanger, or a 'pocket' of air trapped within the unit.
This fault is frequently seen when the heating is first turned on after autumn, as pump components can seize up during months of inactivity.
DIY fix possible
Check that your radiator valves are open to allow water to circulate.Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar).Press the 'Reset' button on the control panel to see if the fault clears.
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A boiler cover plan would cover faults like A08 — no call-out fees, no surprises.
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