BoilerFaultCodesTechnical description
Control box or the heat control module (HCM) is defective – the control box connections need checking
What causes this fault?
This fault occurs when the boiler's main brain loses the ability to talk to its internal memory chip, which contains the specific settings for your appliance. The most common reason is a physical failure of the electronic circuits or a loose connection between the internal control modules that prevents the boiler from identifying itself. Because the boiler no longer knows its own safety parameters, 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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