BoilerFaultCodes E786 Medium
Boiler Fault Code E786
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code E786 appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's front cover is not properly attached or secured, which acts as a safety disconnect to prevent the unit from running while it is open. (As reported on Navien NCB 28 HE)
Pick your boiler brand for the E786 fix
Source
Information for the E786 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 27 April 2026