Your boiler's main internal computer has developed a technical fault and can no longer communicate with the rest of the system.

Controller ABM03B error – controller has an internal error

What causes this fault?

This fault occurs when the boiler's central control board suffers a hardware failure, meaning it can no longer send or receive instructions to vital components like the pump or gas valve. The most common reason is that the delicate electrical circuits on the main PCB have burnt out or degraded, often due to age or an unexpected electrical surge.