Low
S.01 on Vaillant ecoTEC Pro 24

Your boiler is currently preparing to provide heating and is going through its normal start-up cycle.

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

Heating mode: Fan start-up. The fan start-up for heating mode is activated.

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s 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 code appears when the boiler's internal computer tells the fan to begin spinning to clear the combustion chamber and prepare for ignition. It is a normal part of the heating cycle and indicates that the system is successfully moving through its safety checks before firing the burner. If the code stays on screen without the boiler firing, it may suggest a mechanical struggle with the fan or a communication delay between internal components.

You may notice this code more frequently during the autumn when you first switch the heating back on after a long summer break.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Avoid the next call-out bill

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