Medium
S.39 on Vaillant ecoTEC plus aquaPLUS

Your boiler has paused because it detected that the water temperature going into your underfloor heating is too high, preventing damage to your floors.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Contact thermostat has been activated (under floor systems)

From this model's manual
Verified against the Vaillant Ecotec Plus Aquaplus installation & service manual, page 38.
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 if your underfloor heating pump is runningEnsure any manual mixing valves for the underfloor heating are not set too highGently bleed air from the underfloor heating manifold to improve circulation

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