Low
d.40 on Vaillant Home System

This is not actually a fault code, but an information screen showing the current temperature of the water heading to your radiators.

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.

Technical description

Heating flow temperature: Current value

DIY fix possible

Press the 'Back' or 'Menu' button to return to the main displayTurn the boiler off and back on again if the screen is stuckNo further action is required as the boiler is functioning normally

Find a Gas Safe engineer
Search the official register →

Related fault codes

d.41View →S.04View →

Related guides you might find useful

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →