Low
d.23 on Vaillant Ecomax Condensing 600/800 series

Your boiler is currently indicating that it is switching between its summer and winter operational modes based on the position of the control dial.

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

Summer/Winter function (control knob)

From this model's manual
Verified against the Vaillant Ecomax Condensing 600 800 Series installation & service manual, page 47.
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

Turn the heating control knob fully to the left and then back to the right to reset its positionSwitch the boiler off at the fused spur for 30 seconds to allow the internal electronics to rebootEnsure the knob is firmly pressed onto its spindle and is not obstructed by the casing

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