Medium
F.78 on Vaillant Atmomax

Your boiler is having trouble communicating with the hot water temperature sensor because of a broken wire or a loose connection.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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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 to DHW outlet sensor at external controller

Engineer required

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

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Related fault codes

F.13View →F.28View →F.77View →

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