BoilerFaultCodesVaillant 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 37 Vaillant models in our database.
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
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like D.41: no call-out fees, no surprise bills.
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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.
- Atmomax
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825 Repair: £120-220
- ecoFIT Pure 830 Repair: £150-250
- ecoFIT Pure 835
- ecoMAX
- ecoMAX 613
- ecoMAX 618
- ecoMAX 622
- ecoMAX 635
- ecoMAX 824E
- ecoMAX 828E
- Ecomax Condensing 600/800 series
- ecoMAX System 612
- ecoTEC
- ecoTEC 65kW Repair: £150-250
- ecoTEC Plus 615
- ecoTEC Plus 620
- ecoTEC Plus 625
- ecoTEC Plus 630
- ecoTEC Plus 635
- ecoTEC Plus 840
- ecoTEC plus aquaPLUS
- ecoTEC Pro / ecoTEC Plus
- ecoTEC sustain
- Home Combi Repair: £120-220
- Home System
- Thermocompact
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828
- Turbomax Plus 828 E
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH
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.
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoMAX manual (PDF)
- Vaillant ecoMAX System 612 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026