BoilerFaultCodesTechnical description
Accesory Module is blocking burner operation
What causes this fault?
This fault occurs when an external device connected to the boiler, such as a smart thermostat or a wireless receiver, sends a signal to stop the burner from firing. The most common reason is a loss of communication between your thermostat and the boiler, often caused by dead batteries or a signal interference. Essentially, the boiler is waiting for a 'go' signal from your controls that never arrives or is being actively blocked.
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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