BoilerFaultCodesYour boiler's internal computer parts have lost their identity settings or been replaced incorrectly, meaning the system can no longer communicate with itself to operate.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No valid DSN in display and/or mainboard | Spare part failure display and maiboard interchanged at same time and device specific number not adjusted
What causes this fault?
This fault occurs when the boiler's two main computer boards lose their shared identity or fail to recognise each other. It is most commonly caused by a power surge that wipes the memory settings, or if both internal circuit boards are replaced at the same time without the unique device code being manually re-entered.
This fault is often seen following summer storms, as power surges from lightning strikes or grid fluctuations can corrupt the digital memory on the boiler's circuit boards.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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