Low
A.12 on Viessmann Vitodens 222-F B2TF

Your boiler's internal clock has lost power because its small backup battery has run out, which might affect your timed heating schedules.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Real time clock battery flat — replace CR2032 in HMU

From this model's manual
Verified against the Viessmann Vitodens 222 F B2tf installation & service manual.
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

Locate the control unit on the front of the boilerOpen the control unit housing to access the Heat Management Unit (HMU) circuit boardCarefully remove the depleted CR2032 coin cell battery and replace it with a new oneReassemble the unit and reset the time and date on the display

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Related fault codes

F.422View →F.423View →

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