Low
S.4 on Vaillant ecoTEC System

Your boiler is currently operating normally and the burner has successfully lit to provide heat or hot water.

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

Burner ignited

From this model's manual
Verified against the Vaillant Ecotec installation & service manual, page 43.
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 is not actually a fault, but a status message indicating that the boiler’s internal sequence is progressing correctly. It appears when the gas gas has successfully ignited and the burner is currently producing heat for your radiators or hot water. If your boiler seems stuck on this code without producing heat, it may be waiting for a signal from the thermostat or internal sensors.

DIY fix possible

No action is required as this is a status code, not an error.Monitor the boiler to ensure it transitions to other 'S' codes as demand changes.If the code persists without heating being delivered, check that your thermostat is turned up.

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