BoilerFaultCodesTechnical description
Accesory Module is blocking burner operation
What causes this fault?
This fault occurs when an external control device, such as an additional wiring center or a specific zone controller, tells the boiler to stop running for safety or logic reasons. The most common reason is a communication error between the main boiler brain and an add-on expansion module that manages extra heating zones. It suggests that while the boiler itself may be healthy, the external parts controlling it have detected a conflict or a hardware failure.
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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