Medium
D.017 on Vaillant ecoTEC Plus 836

Your boiler is having difficulty communicating with your heating controls or thermostat, which may prevent your radiators from switching on or off as expected.

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

Heatingcontroltype

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 73.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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