Low
d.23 on Vaillant Thermocompact

Your boiler is simply indicating whether it is set to provide both heating and hot water or just hot water.

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) 1 = winter; 0 = summer

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 radiator dial or winter/summer switch on the front control panel.Turn the dial to the '1' position if you want the heating to be active.Turn the dial to the '0' position if you only want hot water for taps and showers.

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All 121 fault codes on the Thermocompact

Seeing a different code? Every code this model can display, in one place.

22.D24.D33.S35.SBurner lock out indicatord.00d.01d.02d.05d.07d.08d.10d.11d.21D.22D.24d.25d.30d.33d.34d.35d.37d.40d.41d.50d.60d.61d.64d.65d.67d.68d.69d.71d.72d.73d.75d.76d.80d.81d.82d.83Er.1Er.2Er.3Er.4Er.5Er.6Er.7Er.8Er.9Er.10Er.11Er.12Er.13Er.14Er.15Er.16Er.17F.00F.01F.10F.11F.20F.22F.23F.24F.27F.28F.29F.32F.33F.37F.41F.42F.43F.60F.61F.62F.63F.64F.65F.66F.67F22P1P2P3P11P12P13S.00S.01S.02S.03S.04S.05S.07S.08S.10S.11S.13S.14S.16S.17S.20S.21S.23S.24S.27S.28S.30S.31S.32S.33S.34S.36S.39S.52S.53S.54

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