High
F.78 on Vaillant ecoTEC Pro 30

Your boiler has lost communication with the device that monitors your hot water temperature, causing it to stop producing hot water.

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

Interruption to DHW outlet sensor at the external controller UK link box is connected, but hot water NTC not bridged

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.77View →F.78View →

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