Low
S.108 on Vaillant Home System

Your boiler is briefly clearing out the air inside to ensure a safe burn before it starts the heating process.

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

Purging the combustion chamber, fan in operation

From this model's manual
Verified against the Vaillant Home System installation & service manual, page 33.
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

Wait for up to 15 minutes as this is a normal part of the boiler's startup routineCheck if the display changes to a different code after the fan stopsEnsure there is credit on your gas meter if you have a prepay system

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