D.41 Low

Vaillant D.41 Fault Code

Also written as D41 — same fault.

The Vaillant D.41 fault code means: your boiler is displaying the current temperature of the water returning from your radiators rather than indicating a fault.. It appears on 28 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: Return temperature actual value

What causes the Vaillant D.41 fault?

This is not actually a fault, but rather a status message indicating that the boiler is currently measuring and displaying the temperature of the water coming back from your radiators. It occurs during normal operation when the control system or an engineer has requested to see the live return temperature data on the screen. Your boiler will continue to provide heating and hot water as normal while this code is visible.

DIY fix possible

Check if the display returns to the normal pressure or temperature reading after a few minutesPress the 'i' button to exit the information menu if you have accidentally entered itNo further action is required if the boiler is heating your home correctly

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Vaillant models that show the D.41 fault code

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

Source

Vaillant D.41 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 27 April 2026