13 Low

Viessmann 13 Fault Code

The Viessmann 13 fault code means: your boiler has lost its connection to the outdoor weather sensor, which means it may not know how hard it needs to work to heat your home efficiently.. It appears on 1 Viessmann model in our database.

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: Lead break, outside temperature sensor
Typical repair cost £100-£190 (including labour)

Engineer required

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

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Viessmann models that show the 13 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Viessmann 13 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026