Viessmann D6 Error ((install)) Today

The Viessmann D6 error code! Let's dive into what it means and how to troubleshoot it.

Step 3: Inspect for Water Leaks

Look at the top of the boiler casing and around the pump. Any drips or signs of rust near the control box? If yes, the leak must be fixed first; otherwise, new boards will fail again.

1. At the Thermostat: Remove the thermostat from the wall backing plate. Check that the wires are securely screwed into the terminals and none have come loose.
2. At the Boiler:

   PCB AssessmentIn rare cases, the sensor and wiring are fine, but the terminal on the PCB is faulty. This is the most expensive fix, as it involves replacing the main control board of the boiler. Can You Run the Boiler with a D6 Error?