BoilerFaultCodesTechnical description
No external operating mode changeover via external extension
What causes this fault?
This fault occurs when the boiler loses its physical connection to an external accessory, such as a plug-in extension module or a third-party controller. It is usually caused by a loose communication wire or a hardware failure within the interface module that handles external commands. While the boiler typically continues to heat, it can no longer receive specific instructions to change its operating mode from these outside devices.
DIY fix possible
Check that any external thermostats or control hubs are powered onEnsure your home Wi-Fi or internet connection is stable if using smart controlsReset the boiler to see if the communication link restores itself
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