Fan operation indicator Low

Vaillant Fan operation indicator Fault Code

Also written as FANOPERATIONINDICATOR — same fault.

The Vaillant Fan operation indicator fault code means: your boiler's fan system is running correctly to safely remove exhaust gases, and the indicator light is simply confirming that this part of the startup process is working as intended.. It appears on 2 Vaillant models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Once the fan and flue system has proved itself, the fan operation indicator will light.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Vaillant models that show the Fan operation indicator fault code

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

Source

Vaillant Fan operation indicator fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026