D.80 Low

Vaillant D.80 Fault Code

Also written as D80 — same fault.

The Vaillant D.80 fault code means: this is not a fault; it is simply a diagnostic screen displaying how many hours your boiler has spent running the central heating.. It appears on 30 Vaillant models 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: Operating hours heating

What causes the Vaillant D.80 fault?

This is not a mechanical failure or a sign of a broken part. It is a diagnostic status code that appears when you access the information menu to track how much work the boiler has done. The display simply shows the total cumulative number of hours the system has been active in central heating mode since it was first installed.

DIY fix possible

Press the 'Back' or 'Menu' button to return to the main displayNo further action is required as this is an information message

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Vaillant models that show the D.80 fault code

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

Source

Vaillant D.80 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

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