Low
d.40 on Vaillant Turbomax 824/828

This code is simply a status display showing the current temperature of the water flowing through your boiler's internal pipes, not an actual fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Actual flow temperature

From this model's manual
Verified against the Vaillant Turbomax 824 828 installation & service manual, page 39.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check your boiler display manual to see if you have accidentally entered the diagnostic or settings menu.Press the 'i' button on the front panel to toggle the display back to the standard operating mode.No physical repairs are required as the boiler is functioning normally.

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