BoilerFaultCodesVaillant S.14 Fault Code
Also written as S14 — same fault.
The Vaillant S.14 fault code means: your boiler is operating normally and has successfully lit the flame to heat your water or radiators.. It appears on 45 Vaillant models in our database.
Technical description: Burner ignited
What causes the Vaillant S.14 fault?
This fault occurs when the boiler's internal flow sensor incorrectly detects that water is running through the hot water pipes, even when all your taps are closed. The most common reason is a sticking internal component or a faulty sensor that is sending a false signal to the boiler's brain. Because the boiler thinks you are prioritising a hot bath or shower, it refuses to switch over to provide heat for your radiators.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like S.14: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Vaillant models that show the S.14 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £120-280
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoFIT sustain 615
- ecoFIT sustain 618
- ecoFIT sustain 630
- ecoFIT sustain 830
- ecoMAX
- ecoMAX 613
- ecoMAX 618
- ecoMAX 622
- ecoMAX 635
- Ecomax Condensing 600/800 series
- ecoMAX System 612
- ecoTEC
- ecoTEC exclusive
- ecoTEC exclusive 627
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC plus 637
- ecoTEC Plus 826
- ecoTEC Plus 832
- ecoTEC Plus 840
- ecoTEC Plus 938
- ecoTEC plus aquaPLUS
- ecoTEC Pro
- ecoTEC Pro / ecoTEC Plus
- ecoTEC Pro 24
- ecoTEC Pro 28
- ecoTEC Pro 30
- ecoTEC sustain
- Home Combi
- Home System
- Thermocompact
- 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.14 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 835 manual (PDF)
- Vaillant ecoFIT sustain 630 manual (PDF)
- Vaillant ecoFIT sustain 830 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026