n9 High

Boiler Fault Code n9

Also written as N9 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code n9 appears across 2 boiler brands and 2 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is currently unable to operate because it has detected an issue with the internal computer software or its communication with the display panel. (As reported on Protherm 100EC)

Pick your boiler brand for the n9 fix

Glow-worm n9 1 model Protherm n9 1 model

Source

Information for the n9 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026