BoilerFaultCodesTechnical description
Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
What causes this fault?
This fault occurs when the boiler's internal computer chips lose the ability to talk to each other, often due to a physical failure in the circuitry. The most common reason is that the Heat Control Module has worn out or developed a loose connection, meaning the boiler can no longer safely manage the heating process. In some cases, a power surge or general age-related degradation of the main control board is the root cause.
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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