How much does it cost to fix Navien error code 004?

Typical repair cost for the Navien 004 fault is £120-250 including labour.

004 High

Navien 004 Fault Code

Q: What does the Navien 004 fault code mean?

Your boiler has detected a failure to ignite or a loss of flame, meaning it cannot start the heating process successfully.

The Navien 004 fault code means: your boiler has detected a failure to ignite or a loss of flame, meaning it cannot start the heating process successfully.. It appears on 7 Navien models in our database.

Technical description: Error 004

Typical repair cost £120-250 (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 004 fault code

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

NCB Repair: £120-250
NCB 28 HE Repair: £150-300
NCB 35 HE Repair: £150-300
NCB 40 HE Repair: £150-300
NCB CE Repair: £120-£250
NCB H Repair: £150-300
NHB 29 Repair: £150-300

Source

Navien 004 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