Low
10 on Viessmann Vitodens 300-W

Your boiler's outside temperature sensor has developed an electrical fault, causing the system to behave as if it is exactly 0°C outdoors regardless of the actual 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

Controls according to 0°C outside temperature: Outside temperature sensor shorted out

From this model's manual
Verified against the Viessmann Vitodens 200 W installation & service manual, page 92.
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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