Low
N.100 on Vaillant ecoTEC plus System

Your boiler has lost the connection to the thermometer placed outside your home, so it can no longer automatically adjust your heating based on the weather.

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.

What the manual says

Manufacturer manual

The signal for the outdoor temperature sensor has been interrupted.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 94.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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