Low
d.18 on Vaillant ecoFIT Pure 435

This is a settings status showing whether your pump stays on longer for extra comfort or switches off sooner to save energy, rather than an actual fault code.

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

Pump overrun operating mode (1=Comfort, 3=Eco)

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 30.
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

Navigate to the installer level menu (code 17)Locate diagnostic code d.18Select '1' if you want the pump to run longer for better heat distributionSelect '3' if you want the pump to stop sooner to save electricity

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