Low
S.05 on Vaillant ecoTEC Plus 938

Your boiler is briefly keeping the internal fan and pump running to safely cool down the heat exchanger after a heating cycle.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Heatingmode:Pump/fanoverrun

From this model's manual
Verified against the Vaillant Ecotec Plus 826 installation & service manual, page 47.
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 a normal part of the boiler's operation and occurs when the heating has finished its cycle. The boiler keeps the internal pump and fan running for a few minutes to dissipate residual heat and safely cool down the internal components. It is not a breakdown and the system will resume normal operation as soon as the cooling process is complete.

DIY fix possible

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

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