Low
d.66 on Vaillant ecoFIT Pure 835

Your boiler has simply turned on its 'comfort' feature which keeps 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.

Technical description

Activation of the warm start function for hot water

DIY fix possible

Locate the hot water temperature dial or buttons on the control panelTurn the dial fully to the right to enable 'Comfort' mode, or fully to the left then back to your desired temperature to reset the stateConsult your manual to toggle the warm-start function off if you prefer to save energy

Find a Gas Safe engineer
Search the official register →

Related fault codes

d.67View →

Related guides you might find useful

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →