BoilerFaultCodesViessmann 88:1 Fault Code
Also written as 881 — same fault.
The Viessmann 88:1 fault code means: your boiler's control panel has switched from celsius to fahrenheit, meaning temperatures are being displayed using a different measurement system rather than showing a mechanical fault.. It appears on 5 Viessmann models in our database.
Technical description: Temperature display in Fahrenheit
What causes the Viessmann 88:1 fault?
This happens when the boiler's internal control unit has been adjusted to display temperature units used in the United States rather than the UK standard. It is usually triggered by someone accidentally changing the display settings within the user menu or during a recent service. It does not indicate a mechanical failure or a safety risk to your heating system.
DIY fix possible
Navigate to the boiler's settings menu using the control dial or touch interface.Look for the 'Display' or 'Configuration' sub-menu.Locate the temperature unit setting and change it back from '°F' to '°C'.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Viessmann models that show the 88:1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 88:1 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 27 April 2026