BoilerFaultCodesTechnical description
Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked
What causes this fault?
This fault occurs when the boiler's internal computer brain loses its connection with the specific data chip that holds its operating instructions. It is usually caused by a physical failure of the Heat Control Module chip or a breakdown in the electrical circuits on the main control board. Because the boiler no longer knows its own safety limits, it shuts down immediately to prevent damage.
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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