Low
A.12 on Viessmann Vitodens 200-W B2HF System

Your boiler's internal clock has lost its memory because a small backup battery has run out of power.

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 battery in HMU

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 200 W B2kf Combi 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 panel (HMU) on the front of the boilerIdentify the small circular battery slot containing the CR2032 coin cellCarefully swap the old battery for a new CR2032 battery and reset the time and date

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Related fault codes

A.13View →F.420View →

All 141 fault codes on the Vitodens 200-W B2HF System

Seeing a different code? Every code this model can display, in one place.

377A.11A.18A.20A.21F.5F.7F.8F.9F.10F.11F.12F.13F.14F.15F.16F.29F.30F.49F.50F.57F.58F.59F.62F.63F.67F.68F.69F.70F.71F.72F.73F.74F.77F.89F.91F.92F.94F.100F.104F.142F.160F.161F.163F.182F.183F.184F.185F.299F.342F.345F.346F.348F.349F.350F.351F.352F.353F.354F.355F.357F.359F.361F.365F.366F.367F.369F.370F.372F.373F.377F.378F.379F.380F.381F.382F.383F.384F.385F.386F.387F.388F.395F.396F.399F.400F.401F.402F.403F.404F.405F.406F.408F.410F.416F.417F.418F.425F.430F.446F.447F.448F.449F.450F.451F.452F.453F.454F.455F.456F.457F.458F.462F.463F.464F.467F.468F.471F.473F.474F.517F.527F.528F.530F.540F.544F.545F.546F.547F.548F.549I.56I.57I.59P.1P.4P.8S.60S.74S.75

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