BoilerFaultCodesTechnical description
Control / no flow thermistor fault
What causes this fault?
This fault occurs when the boiler detects a sudden, unexpected rise in temperature because water isn't moving through the heat exchanger quickly enough. The most common reasons are a failed internal pump, a physical blockage like sludge in the pipework, or a faulty sensor that is sending incorrect temperature readings to the main computer.
This issue often appears when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
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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