Low
d.28 on Vaillant ecoFIT Pure 435

Your boiler is notifying you of an issue with how an optional internal or external control module is communicating with the main system.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Function of relay 2 (multi-functional module)

Engineer required

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

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Related fault codes

d.27View →F.77View →

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