BoilerFaultCodesNavien 289 Fault Code
The Navien 289 fault code means: your boiler has detected an internal cooling system issue and has automatically shut down to prevent damage from overheating.. It appears on 1 Navien model in our database.
Technical description: 289:WCS overt + inner iron: Water cooled seal thermostat has operated and Inner iron thermostat has operated.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Navien models that show the 289 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Navien 289 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 7 July 2026