Low
18 on Viessmann Vitodens 100-W WB1B

Your boiler has lost the connection to the thermometer installed outside your home, so it cannot automatically adjust your heating based on the outdoor 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

Break, outside temperature sensor

From this model's manual
Verified against the Viessmann Vitodens 100 W Wb1b System installation & service manual, page 33.
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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