E786 Medium

Navien E786 Fault Code

The Navien E786 fault code means: 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.. It appears on 4 Navien models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Improper front panel

DIY fix possible

Switch off the power to the boilerRemove the front cover and ensure no wires are pinchedReplace the front cover, ensuring it is flush and firmly locked in place with all screws tightened

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Navien models that show the E786 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Navien E786 fault code information on this page is sourced and cross-checked against the official Navien service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026