BoilerFaultCodesTechnical description
Outdoor Unit, Air to Refrigerant Heat Exchanger Outlet Thermistor (T3) Error
What causes this fault?
This fault occurs when the heat pump’s control board loses communication with the sensor that monitors the temperature of the coils outside. This usually happens because the sensor itself has failed internally or the electrical wiring has become corroded or loose over time. Without this specific data, the system cannot safely manage the heating process and shuts down to prevent damage.
This issue is more frequent during winter, as extreme cold and moisture can accelerate the degradation of exposed electrical sensors and wiring.
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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