Low
d.16 on Vaillant ecoFIT pure

This is a status indicator showing whether your external room thermostat is currently asking the boiler to provide heating or stay off.

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

Status of the 24V room thermostat (off=Heating off, on=Heating on)

DIY fix possible

Check if your room thermostat is turned up high enough to trigger a heat demandReplace the batteries in your wireless wall thermostat if the screen is blankEnsure your heating programmer or app is set to an 'On' period

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