S.06 High

Vaillant S.06 Fault Code

Also written as S06 — same fault.

The Vaillant S.06 fault code means: your boiler is staying in a cooling-down phase for too long because it thinks the fan is still spinning after it should have stopped.. It appears on 25 Vaillant models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Heating mode – fan overrun error

What causes the Vaillant S.06 fault?

This fault occurs when the boiler's control board expects the fan to stop spinning after a heating cycle, but it continues to receive a signal that the fan is still rotating. The most common reason is a communication error between the fan and the main circuit board, often caused by a faulty sensor inside the fan or a sticking internal component. In some cases, a damaged wiring harness or moisture on the electronics can prevent the fan from shutting down correctly.

Typical repair cost £150-£450 (including labour)

DIY fix possible

Press the reset button (indicated by a flame with a cross through it)Turn the boiler power off at the fused spur switch, wait 30 seconds, and turn it back onCheck for any visible obstructions or debris around the external flue pipe terminal

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Vaillant models that show the S.06 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant S.06 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026