BoilerFaultCodesYour boiler has stopped working because a sensor that monitors the temperature of the water leaving the unit has failed or disconnected.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow NTC fault
What causes this fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that monitors the temperature of the water sent to your radiators. The most common reason is that the sensor has physically failed due to age or internal wear, though it can also be caused by a loose wire or moisture damaging the electrical connection.
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 F10 — no call-out fees, no surprises.
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Glow-worm Flexicom 18sx 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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