Technical Service Bulletin

Boiler displays fault code A2 or A4 on Vitodens 200

Applies to: Vitodens 200, WB2B Series (all models)

Important Disclaimer

The information in this bulletin is intended exclusively for licensed heating contractors, and is NOT intended for the end user. This material is NOT intended to take the place of the information contained in the manuals shipped with the product.

Use of this information by unqualified personnel may result in property damage, personal injury or death.

End users are asked to contact a qualified contractor for all installation and service work. If you need assistance finding a contractor in your area, contact your Viessmann Sales Representative, or use our Contractor Locator.

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The boiler is operating, but fault code "A2" or "A4" is displayed on the boiler control.
Fault will not clear when the reset button is pressed.



Coding addresses not listed in the manual were mistakenly changed from the factory default settings.



If fault code A2 is displayed, then change the value at coding address "0D" to "0".
If fault code A4 is displayed, then change the value at coding address "0E" to "0".
Then press the reset button to restart the boiler.


Viessmann Technical Services


Bulletin ID:


Date issued:

October 12, 2016

Updated on:

January 12, 2018

Revision #:


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