E407 High

Navien E407 Fault Code

The Navien E407 fault code means: your boiler is struggling to accurately measure the temperature of the hot water leaving the unit because a sensor has stopped communicating correctly.. It appears on 5 Navien models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: DHW Outlet thermistor Open or Short Circuit
Typical repair cost £120-220 (including labour)

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 E407 fault code

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

Source

Navien E407 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