Viessmann D6 Error ((free)) -

Note: This is especially common in winter.

A: Diagnosing a loose wire: ~$150 service call. Replacing a BCU board: $400–$800 depending on model and region. viessmann d6 error

Inspect the exhaust pipe on the outside of your building. Ensure it is completely clear of leaves, snow, ice, or animal nests. A blocked exhaust prevents proper airflow and triggers the error. 2. Reset the Boiler Note: This is especially common in winter

The small plastic tubes connecting the fan to the pressure switch may be cracked, blocked by moisture (condensation), or disconnected. Control Board (PCB) Issue: Inspect the exhaust pipe on the outside of your building

The display panel itself (sometimes called the "Vitotrol" or front fascia) may have failed due to a power surge or aged electronics.

If the extension module (EA1) itself is faulty, it will need a professional replacement.

However, if the boiler is and you have: