Low
D.23 on Vaillant Atmomax

Your boiler is currently set to summer mode, which means it will provide hot water but has temporarily disabled the central heating.

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

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
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

Locate the temperature control knob for the heating circuit on the front panel.Turn the dial clockwise away from the 'Sun' icon or leftmost position to your desired temperature setting.Check if the radiators begin to warm up after a few minutes.

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