Low
d.66 on Vaillant ecoFIT Pure 435

Your boiler is notifying you that the 'warm start' feature is active, which keeps a small amount of water pre-heated so it reaches your taps faster.

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

Activation of the warm start function for hot water

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 31.
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 'comfort' or 'warm start' setting in the user menuSwitch the setting to 'Off' if you wish to save energy and do not mind waiting slightly longer for hot waterNo action is required if you prefer to have hot water available quickly

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