Your boiler’s main computer brain has developed an internal electrical error and has stopped the unit from working for safety.

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 an internal hardware failure, meaning the electronic components can no longer talk to each other correctly. The most common reason is historical heat stress or a power surge that has damaged the delicate circuitry inside the module, causing it to shut down for safety.