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 35 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.
- Atmomax Repair: £90-160
- ecoFIT Pure 412 Repair: £120-220
- ecoFIT Pure 418 Repair: £120-200
- ecoFIT Pure 425 Repair: £120-200
- ecoFIT Pure 435 Repair: £120-200
- ecoFIT Pure 825 Repair: £120-220
- ecoFIT Pure 830 Repair: £120-220
- ecoFIT Pure 835 Repair: £120-200
- 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 824E Repair: £110-190
- ecoMAX 828E Repair: £110-190
- Ecomax Condensing 600/800 series Repair: £120-200
- ecoMAX Pro 28E Repair: £250-450
- ecoMAX System 612 Repair: £110-190
- ecoTEC Repair: £90-£180
- ecoTEC 65kW Repair: £120-200
- ecoTEC exclusive Repair: £120-£200
- ecoTEC Plus 610 Repair: £120-220
- ecoTEC Plus 615 Repair: £90-160
- ecoTEC Plus 620 Repair: £90-160
- ecoTEC Plus 625 Repair: £90-160
- ecoTEC Plus 630 Repair: £90-160
- ecoTEC Plus 635 Repair: £90-160
- ecoTEC Plus 826 Repair: £120-220
- ecoTEC Plus 840 Repair: £90-160
- ecoTEC Plus 938 Repair: £90-160
- ecoTEC plus aquaPLUS Repair: £100-180
- ecoTEC Pro / ecoTEC Plus Repair: £120-200
- ecoTEC sustain Repair: £90-160
- Home Combi Repair: £120-220
- Home System Repair: £90-160
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 412 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoMAX manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026