BoilerFaultCodesVaillant F.13 Fault Code
Also written as F13 — same fault.
The Vaillant F.13 fault code means: your boiler has detected an electrical fault with the internal sensor that monitors the temperature of its hot water storage tank.. It appears on 38 Vaillant models in our database.
Technical description: Shortcircuit:Cylindersensor. Combinationproduct:Warmstartsensor/cylindersensorshortcircuit. CombinationproductwithactoSTOR:Shortcircuitcylindersensor(NTC) onlyincombinationwithF.91. NTCdefective,shortcircuitincableharness,cable/housing
What causes the Vaillant F.13 fault?
This fault occurs when the boiler's control board receives a scrambled or impossible electrical signal from the sensor that monitors your hot water storage. The most common reason is that the sensor has failed internally or the protective coating on the wiring has worn through, causing an electrical 'short' against the metal casing. It can also be caused by water or moisture getting into the electrical plug, which disrupts the connection.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Vaillant models that show the F.13 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412 Repair: £120-220
- ecoFIT Pure 418 Repair: £120-200
- ecoFIT Pure 425 Repair: £120-200
- ecoFIT Pure 435 Repair: £90-180
- ecoFIT pure 612 Repair: £120-220
- ecoFIT pure 615 Repair: £120-220
- ecoFIT pure 618 Repair: £120-220
- ecoFIT pure 630 Repair: £120-220
- ecoFIT Pure 825 Repair: £120-220
- ecoFIT Pure 830 Repair: £120-220
- ecoFIT Pure 835 Repair: £120-200
- ecoFIT sustain 415 Repair: £90-180
- ecoFIT sustain 418 Repair: £90-180
- ecoFIT sustain 430 Repair: £90-180
- ecoFIT sustain 615 Repair: £90-180
- ecoFIT sustain 618 Repair: £90-180
- ecoFIT sustain 630 Repair: £90-180
- ecoFIT sustain 825 Repair: £90-180
- ecoFIT sustain 830 Repair: £90-180
- ecoFIT sustain 835 Repair: £90-180
- ecoMAX Repair: £90-180
- ecoMAX 613 Repair: £110-190
- ecoMAX 618 Repair: £110-190
- ecoMAX 622 Repair: £110-190
- ecoMAX 635 Repair: £110-190
- ecoMAX 824/2 E Repair: £110-190
- ecoMAX 828/2 E Repair: £110-190
- ecoMAX 835 E Repair: £110-190
- Ecomax Condensing 600/800 series Repair: £120-200
- ecoMAX Pro 28E Repair: £250-450
- ecoTEC exclusive Repair: £120-£200
- ecoTEC plus Repair: £90-£180
- ecoTEC plus VU GB 656/4-5 A Repair: £120-200
- ecoTEC sustain Repair: £90-160
- Home Combi 25 Repair: £120-220
- Home Combi 30 Repair: £120-220
- Home Combi 35 Repair: £120-220
- Home Regular 12
Source
Vaillant F.13 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 630 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026