Medium
d.90 on Vaillant ecoFIT Pure 418

Your boiler is having trouble communicating with your wall-mounted thermostat, which means it may not know when to turn the heating on or off.

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

Status of the eBUS room thermostat

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 32.
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 that the batteries in your room thermostat are fresh and fully charged.Ensure the thermostat is not showing a 'low signal' or 'disconnected' warning.Turn the boiler off at the fused spur for 60 seconds to reset the connection, then turn it back on.

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Related fault codes

d.91View →d.96View →

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