How much does it cost to fix Navien error code 012?

Typical repair cost for the Navien 012 fault is £80-150 including labour.

012 High

Navien 012 Fault Code

Q: What does the Navien 012 fault code mean?

Your boiler has detected that it is running out of water inside its internal system, which prevents it from heating your home safely.

The Navien 012 fault code means: your boiler has detected that it is running out of water inside its internal system, which prevents it from heating your home safely.. It appears on 7 Navien models in our database.

Technical description: Error 012

Typical repair cost £80-150 (including labour)

DIY fix possible

Locate the external filling loop, usually a silver flexible hose connected to two valves under the boiler.Gradually open the valves to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valves tightly and restart the boiler.

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Navien models that show the 012 fault code

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

Source

Navien 012 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