Short answer
PCB faults are real but over-diagnosed. Many 'PCB faults' are actually sensor, wiring, earth or supply issues. A genuine fault shows as the board failing to drive outputs it is commanding, failing to read inputs that are verified good, or failing to power up.
Common causes
Water damage from leaks or condensate.
Voltage spikes or poor supply.
Overheated relays or connectors.
Corrupt parameters after power events.
What the engineer checks
Verify the supply, fuses and earth.
Test sensors and outputs independently before blaming the board.
Check for water ingress and burnt connectors.
Repair and prevention
Replace with the correct board, transfer or set parameters for the boiler model and output, and recommission including combustion checks.
Figures are typical for UK natural gas. The current edition of the relevant IGEM standard and the manufacturer's instructions always take precedence on site.
Need this done on site?
Manufacturer support
We diagnose this fault on all major commercial boiler brands:
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