Medium
F.03 on Vaillant ecoTEC exclusive

Your boiler has lost communication with the temperature sensor in your hot water tank, meaning it cannot accurately detect when your water is hot enough.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Interruption:Cylindersensor OnlyinconjunctionwithF.91 NTCdefective,NTCcabledefective,defectiveplugconnectiononNTC,defectiveplugconnectionontheactoSTORelectronics

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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