Your boiler's main internal computer has developed a software or hardware failure and can no longer control the heating and hot water.

There is an internal fault in the Automatic Control Module.

What causes this fault?

This fault occurs when the boiler's main control board experiences a critical internal communication failure or a physical burnout of its circuitry. It is often caused by long-term heat exposure degrading the electronic components or a sudden electrical surge that damages the board's memory chip.