Low
d.23 on Vaillant Home System

Your boiler is currently set to summer mode, which means it will only provide hot water and will not turn the radiators on.

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

Status of the heating demand: off=Heating off (Summer mode), on=Heating on

From this model's manual
Verified against the Vaillant Home System installation & service 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 radiator temperature dial or button on the control panelTurn the dial clockwise or press the button to increase the target temperature above 'Off'Check that your external room thermostat is turned up and calling for heat

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