BoilerFaultCodesYour boiler's temperature sensor for the central heating system has failed or developed a fault, meaning the boiler cannot accurately gauge how hot the water is.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Heating thermistor (NTC) fault
What causes this fault?
This fault occurs when the internal sensor responsible for tracking the temperature of your radiators fails to send a reliable signal to the main control board. The most common reason is that the sensor's internal electrical resistance has drifted out of range due to age or heat degradation, though loose or corroded wiring can also trigger the alert.
This fault is more common in autumn when the heating is turned on for the first time after summer, as the sudden thermal expansion can cause a weakened sensor to fail completely.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like 05 — no call-out fees, no surprises.
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