BoilerFaultCodesVaillant S.05 Fault Code
Also written as S05 — same fault.
The Vaillant S.05 fault code means: your boiler is currently taking a short pause to circulate water and cool down internal parts after a period of heating.. It appears on 19 Vaillant models in our database.
Technical description: Heating mode: Pump/fan overrun. The pump/fan overrun for heating mode is activated.
What causes the Vaillant S.05 fault?
This status occurs when the boiler has finished a central heating cycle and needs to dissipate residual heat from the internal heat exchanger. The pump continues to run to move hot water away from the burner, ensuring the internal components cool down safely and efficiently. It is a programmed safety and maintenance routine rather than a mechanical failure.
DIY fix possible
No action is required as this is a normal operational status message.Wait a few minutes for the timer to finish and the code to disappear.Check that your radiators are turned on to help the heat dissipate more quickly.
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Vaillant models that show the S.05 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoTEC pro
- ecoTEC sustain
- Home Combi 25
- Home Combi 30
- Home Combi 35
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
Source
Vaillant S.05 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 425 manual (PDF)
- Vaillant ecoFIT Pure 435 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026