BoilerFaultCodesYour boiler has switched itself off because it has become too hot inside, usually due to a circulation problem or a component failure.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheat fault: The maximum temperature thermostat has operated.
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit, causing the safety sensors to shut the system down to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage in the heat exchanger caused by a buildup of debris and limescale over time.
This issue often comes to light during the first cold snap of autumn when the heating is turned back on after being idle all summer, which can cause internal parts like the pump to seize.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like F5 — no call-out fees, no surprises.
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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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