BoilerFaultCodesYour boiler is struggling to monitor its temperature correctly because a internal sensor is sending a faulty signal, preventing the heating from working properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Central heating thermistor sensor fault
What causes this fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that monitors water temperature. The most common reason is that the thermistor has physically degraded over time or suffered an electrical failure, meaning it can no longer tell the boiler if the water is safe to heat. In some cases, loose or damaged wiring between the sensor and the main control board can also trigger this specific error.
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 E20 — no call-out fees, no surprises.
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