Low
S.01 on Vaillant Home System

Your boiler is currently preparing to start the heating cycle by running its internal fan to clear out any residual gases.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Heating mode: Advance fan operation

From this model's manual
Verified against the Vaillant Home System installation & service manual, page 32.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

No action is required; this is a normal status message and not a breakdown code.Wait a few moments for the boiler to move to the next stage of operation.Check that your thermostat is calling for heat if the boiler stays on this code for a long period.

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