High Lockout
F.13 on Vaillant ecoTEC exclusive

Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of its hot water storage tank.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Shortcircuit:Cylindersensor | Combinationproduct:Warmstartsensor/cylindersensorshortcircuit CombinationproductwithactoSTOR:Shortcircuitcylindersensor(NTC) onlyincombinationwithF.91 NTCdefective,shortcircuitincableharness,cable/housing

What causes this 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.10View →F.11View →

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