Low
d.39 on Vaillant ecoTEC plus System

Your boiler is simply reporting the current temperature reading from your solar heating system, which is a routine data check rather than a system error.

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

Water temperature in the solar circuit: Current value

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.40View →

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