Medium
S.36 on Vaillant ecoTEC 65kW

Your boiler's external temperature controller is set too low, so the heating system has temporarily stopped working to prevent inefficient operation.

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

Referencesettingforthecontinuouscontroller7-8-9oreBUScontrolleris<20°Candblockstheheatingmode

From this model's manual
Verified against the Vaillant Ecotec 65kw installation & service manual, page 35.
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 your wall-mounted thermostat or heating controller.Increase the target temperature to above 20°C.Check if the controller is correctly connected and has fresh batteries if applicable.

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