BoilerFaultCodesVaillant S.16 Fault Code
Also written as S16 — same fault.
The Vaillant S.16 fault code means: your boiler has detected an issue with the air fan system and has temporarily stopped heating to prevent further damage.. It appears on 47 Vaillant models in our database.
Technical description: DHW mode: Fan overrun
What causes the Vaillant S.16 fault?
This fault occurs when the boiler's control system detects that the fan is spinning but sending back incorrect signals, or it isn't spinning at the speed required for safe combustion. The most common reason is an internal electrical failure within the fan motor itself or a communication glitch between the fan and the main circuit board. Without the fan functioning perfectly to clear exhaust gases, the boiler shuts down as a safety precaution.
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.16: 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.16 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £150-£350
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoFIT sustain 615
- ecoFIT sustain 618
- ecoFIT sustain 630
- ecoMAX
- ecoMAX 613 Repair: £0-80
- ecoMAX 618 Repair: £0-80
- ecoMAX 622 Repair: £0-80
- ecoMAX 635 Repair: £0-80
- Ecomax Condensing 600/800 series
- ecoMAX System 612 Repair: £0-80
- ecoTEC
- ecoTEC exclusive Repair: £250-480
- ecoTEC exclusive 627
- ecoTEC plus 612 Repair: £150-£450
- ecoTEC plus 618 Repair: £150-£450
- ecoTEC Plus 620
- ecoTEC plus 624 Repair: £150-£450
- 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 Repair: £0-120
- 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.16 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 Ecomax Condensing 600/800 series manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026