Medium
FA9 on Viessmann Vitodens 025-W

Your boiler has lost its connection to your smart thermostat or external heating controller.

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

OpenTherm remote control not connected

From this model's manual
Verified against the Viessmann Vitodens 025 W installation & service manual, page 61.
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 if your thermostat batteries need replacingEnsure your internet router and hub are switched on and connectedCheck for loose wires at the thermostat base unit if it is easily accessiblePress the reset button on the boiler control panel

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Related fault codes

F.225View →EbView →

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