BoilerFaultCodesYour boiler has detected that the exhaust gases are getting too hot, so it has shut down as a safety precaution to prevent internal damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue gas temperature is too high.
What causes this fault?
This fault occurs when the internal heat exchanger cannot transfer heat into the water efficiently, causing the waste gases to reach a dangerous temperature. The most common reason is a buildup of limescale or debris inside the heat exchanger, but it can also be caused by a faulty sensor or a damaged burner seal allowing heat to escape where it shouldn't.
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 F003 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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