Low
S.109 on Vaillant ecoFIT Pure 412

Your boiler has entered a temporary sleep mode and is currently not running, likely because it is waiting for a signal from your heating controls.

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

Product's standby mode activated

From this model's manual
Verified against the Vaillant Ecofit Pure 412 installation & service manual, page 29.
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 room thermostat or smart controller to ensure it is set to call for heatTurn the boiler power supply off at the spur for 30 seconds and switch it back onEnsure your heating programmer is set to 'On' rather than 'Off' or 'Standby'

Find a Gas Safe engineer
Search the official register →
Boiler cover options

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

S.108View →S.110View →

Related guides you might find useful

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 →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →