Low
18 on Viessmann Vitodens 100-W

Your boiler has lost the signal from the weather sensor outside your home and is now running on a default setting.

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

Constant mode: Outdoor temperature sensor lead broken

From this model's manual
Verified against the Viessmann Vitodens 100 W installation & service manual.
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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