BoilerFaultCodesTechnical description
Central heating return negative temperature coefficient (NTC) thermostat fault.
What causes this fault?
This fault occurs when the boiler's internal computer receives an illogical or missing signal from the sensor that monitors water returning from your radiators. The most common reason is that the sensor has physically failed or developed a chemical build-up, but it can also be caused by damaged internal wiring or a loose connection.
This fault is more common when the heating is first turned on after summer, as the sudden change in temperature can cause aging sensors to fail.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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