7 Medium

Viessmann 7 Fault Code

The Viessmann 7 fault code means: your boiler is unable to read the temperature of your hot water cylinder, meaning your hot water may not heat up correctly to the set temperature.. It appears on 1 Viessmann model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Lead break, cylinder temperature sensor
Typical repair cost £90-180 (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 7 fault code

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

Source

Viessmann 7 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