BoilerFaultCodesYour boiler has detected a communication problem with its temperature sensor and has stopped running for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Lighting Sequence-Thermistor / Check connection & value
What causes this fault?
This fault occurs when the boiler's control board loses its connection with the temperature sensor, meaning it can no longer monitor how hot the water is getting. The most common reason is that the internal sensor has developed an electrical fault or the wiring connecting it to the main board has become loose or damaged. For safety, the boiler shuts down immediately because it cannot ensure the unit won't overheat.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Simultaneous Fast Flashing (8Hz) — no call-out fees, no surprises.
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