BoilerFaultCodesYour boiler is struggling to monitor the temperature of the water circulating through your radiators, causing the system to stop heating your home.
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 sensor responsible for measuring the temperature of the water in your heating system becomes faulty or loses its connection to the main control board. If the boiler cannot accurately track how hot the water is, it will shut down as a safety precaution to prevents the system from overheating. The most common reason is that the internal component has simply worn out over time or the wiring connecting it has become loose or damaged.
This fault is more common in autumn when the heating is turned on for the first time after summer, as the sudden change in temperature and system pressure can cause an aging sensor to fail.
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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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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