Low Warning
18 on Viessmann Vitodens 100-W / 200-W

Your boiler has lost its connection to the outside temperature sensor, meaning it cannot 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.

Technical description

Controls according to 0°C outside temperature: Outside temperature sensor lead break

What causes this fault?

This fault occurs when the boiler's control board loses the electrical signal from the sensor located on the outside of your home. The most common reason is a broken or corroded wire between the sensor and the boiler, often caused by exposure to the elements or accidental damage. In some cases, the internal components of the sensor itself may have failed due to age.

Engineer required

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

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