Low
18 on Viessmann Vitodens 300-W

Your boiler has lost connection to its outdoor sensor, causing it to think it is freezing outside and potentially making your radiators warmer than necessary.

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

DIY fix possible

Locate the outdoor sensor on your external wallCheck for any visible damage or loose wires leading to the sensor unitEnsure the sensor is not covered by debris or snowReset the boiler to see if the fault clears

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