High
S.39 on Vaillant ecoTEC Pro 30

Your boiler has temporarily stopped firing because a safety switch—often linked to how it drains water or monitors temperature—has triggered a protective shutdown.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

"Burner off contact" has responded (e.g. contact thermostat or condensate pump)

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.22View →F.23View →

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