Technical Service Bulletin

Issue:  Boiler is not responding to a call for heat

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

Vitodens 200, WB2B

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.

By hitting "Yes" below you confirm that you have read, understood and agree to this warning, that you are licensed and hold the current, appropriate licences to work on said equipment in the location and/or jurisdiction of installation.


Boiler is not responding to a call for heat (the burner does not fire at all), no fault is displayed on the boiler control, and coding address "38" has a value of "33".


The internal, non-replaceable fuse in the boiler control console has failed.

This can be caused by:

1. An electrical short at the gas valve terminals, if they have become wet. Burning or discoloration of the terminals will usually accompany this failure.

2. A faulty gas valve or radial fan.

3. An internal fault within the control.


Viessmann recommends that the control console, coding card and gas valve be replaced as a group, to prevent one faulty component from damaging others.

In addition:

1. If there was an electrical short at the gas valve terminals, then the gas valve wiring harness must be replaced.

2. Check if the radial fan is faulty, and replace it if necessary.

3. Check if any other outside influences are negatively affecting the control.

Viessmann Technical Services 

Bulletin ID:     TSB-006

Date issued:   Nov 15, 2016

Updated on:   Nov 30, 2017

Revision #:      02