Low
d.35 on Vaillant ecoTEC plus System

Your boiler is currently monitoring or moving the internal switch that directs hot water to either your radiators or your taps.

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

Position of the diverter valve: 0=Heating, 40=Mid-position (parallel operation), 100=Domestic hot water

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related fault codes

F.75View →F.73View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →