The indicates a communication or external reporting fault typically involving the EA1 extension module or an external safety device. While it implies an external component issue rather than a core boiler failure, resolving it requires a systematic approach.
The boiler's control system has detected that the fan is either not running at the required speed or the air pressure switch has not closed. This is a safety feature designed to ensure that exhaust gases are being properly vented before the burner ignites. Common Causes Faulty Fan Motor: The fan is stuck, disconnected, or the motor has failed. Air Pressure Switch Failure: viessmann d6 error
To his surprise, the boiler fired up normally, and the D6 error code disappeared! It turned out that a previous configuration change had caused the issue, and resetting the settings resolved the problem. Viessmann D6 error The indicates a communication or
✅ This is a very common winter cause of D6. You suspect the PCB (Printed Circuit Board) inside