Your boiler's main control board has encountered a software or electrical error and is unable to operate the system safely.

Internal fault (PCB)

What causes this fault?

This fault occurs when the boiler's internal computer experiences a breakdown in communication or a hardware failure on its circuitry. The most common reason is electrical degradation of the components on the board over time, or a sudden power surge that has damaged the delicate microprocessors required to control the boiler safely.