BoilerFaultCodesTechnical description
Return thermistor fault
What causes this fault?
This fault occurs when the sensor responsible for measuring the temperature of the water flowing back into the boiler fails or sends an unreadable signal to the main control board. The most common reason is that the internal components of the thermistor have degraded over time, though it can also be caused by loose or damaged electrical connections. Since the boiler can no longer safely monitor its own temperature, it shuts down to prevent overheating.
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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