BoilerFaultCodesYour boiler is firing up and staying on even when you haven't turned on your heating or hot water taps.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Autofroststat. Board fault.
What causes this fault?
This fault occurs when the boiler's internal controls incorrectly signal that heat is needed, usually because the frost protection sensor has failed and thinks the unit is freezing. It can also be caused by a communication error on the main circuit board, which effectively gets stuck in the 'on' position. Because the system believes it is protecting itself from ice damage, it will continue to burn fuel even if your thermostat is turned off.
This fault is more common during the winter months when colder ambient temperatures are more likely to trigger a malfunctioning frost thermistor.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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