Low
D.35 on Vaillant ecoTEC System

Your boiler is currently switching over between its heating and hot water functions.

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

Not relevant

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

What causes this fault?

This status occurs when the internal diverter valve physically moves to switch the flow of heated water between your radiators and your hot water taps. It is a normal mechanical process where the boiler pauses momentarily to ensure heat is directed to the right place. You will see this on the screen briefly during transitions, such as right after you turn off a hot tap while the heating is on.

DIY fix possible

No action is required as this is a normal status message rather than a fault.Wait a few moments for the boiler to complete its cycle.If the boiler appears stuck, try a simple reset by pressing the flame button.

Find a Gas Safe engineer
Search the official register →

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

Related guides you might find useful