BoilerFaultCodesYour boiler's temperature sensor has failed or is disconnected, meaning the system cannot accurately measure how hot the water is for your heating.
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 error
What causes this fault?
This fault occurs when the boiler's internal computer loses communication with the temperature sensor that monitors your central heating water. The most common reason is that the sensor has electronically failed or 'drifted' over time, but it can also be caused by loose or damaged wiring connecting the sensor to the main control board.
This fault is more common in autumn when systems are turned back on after summer, as the sudden change in temperature and increased demand can cause an aging sensor to finally fail.
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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