Medium
D.028 on Vaillant ecoTEC Pro 28

Your boiler is having trouble communicating with an external add-on component, such as a remote controller or an extra pump, which is preventing it from operating correctly.

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

Accessory relay 2

From this model's manual
Verified against the Vaillant Ecotec Pro installation & service manual, page 43.
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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