BoilerFaultCodesYour boiler has detected a problem with the internal temperature sensor that monitors the water leaving the unit, causing it to shut down as a safety precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow Thermistor Fault
What causes this fault?
This fault occurs when the sensor responsible for measuring the heat of the water leaving your boiler fails to send a correct signal to the main control board. The most common reason is that the sensor has physically degraded or developed an electrical short, but it can also be caused by loose wiring or a glitch in the boiler's internal computer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like L4 — 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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