BoilerFaultCodesYour boiler's internal temperature sensor has stopped sending a reliable signal, which means the system cannot safely monitor how hot the water is getting.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Thermistor resistance not between 0.5kΩ & 20kΩ or wiring fault between PCB and thermistor.
What causes this fault?
This fault occurs when the boiler's internal thermometer, called a thermistor, fails to measure the water temperature correctly. The most common reason is that the sensor has physically degraded over time or developed an electrical short, though it can also be caused by loose or corroded wiring to the main control board.
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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