BoilerFaultCodesTechnical description
BMM fault.
What causes this fault?
This fault occurs when the two internal computers inside your boiler stop talking to each other. It is usually caused by a physical failure of the electronic circuits or a loose connection in the internal wiring, meaning the boiler can no longer verify it is operating safely. Because the system can't confirm vital safety checks, it shuts down completely as a protective measure.
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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