How much does it cost to fix Navien error code E407?

Typical repair cost for the Navien E407 fault is £150-250 including labour.

E407 High

Navien E407 Fault Code

Q: What does the Navien E407 fault code mean?

Your boiler is struggling to accurately measure the temperature of the water circulating through your radiators, so it has safely shut itself down to prevent potential overheating.

The Navien E407 fault code means: your boiler is struggling to accurately measure the temperature of the water circulating through your radiators, so it has safely shut itself down to prevent potential overheating.. It appears on 7 Navien models in our database.

Technical description: Thermistor failure or inaccurate water temperatures at the boiler's space heating outlet/inlet

Typical repair cost £150-250 (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 27 April 2026