BoilerFaultCodesYour boiler's internal temperature sensor has stopped sending a reliable signal, which means the system cannot safely monitor how hot the water is for your radiators.
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 NTC Fault
What causes this fault?
This fault occurs when the thermistor, a small sensor that monitors water temperature, fails or provides an incorrect electrical reading to the boiler's control board. The most common reason is internal degradation over time or loose wiring connections, which prevents the boiler from knowing when to safely turn the burner on or off.
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 E20 — 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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