Viessmann D6 Error !exclusive! – Editor's Choice

Note: Prices are averages for UK/EU/US markets. Always get a fixed quote before work begins.

If all mechanical parts, pressures, and wires are functional, the engineer will test the burner control unit. If the board is faulty, a full PCB replacement will be required. How to Prevent the D6 Error from Returning

Have you fixed a D6 error another way? Let us know in the comments below.

Make sure to have your serial number ready when you call for service to ensure the repair is covered.

: Ensure your central heating system digital pressure gauge reads within the optimal 1.5 to 2.0 bar range. Low pressure naturally reduces flow efficiency. viessmann d6 error

Before opening any casing on the boiler, ensure the power is isolated. If you are uncomfortable with electrical wiring, contact a Gas Safe registered engineer.

This is where the D6 error is most frequently reported. It appears on models like the Vitocal 200-S, Vitocal 222-S, and Vitocal 300A.

Gas boiler internals should only be modified by a registered professional (such as a Gas Safe registered engineer). However, you can perform basic external checks before calling a technician. Step 1: Perform a System Reset

Do you hear the right before the D6 error appears? Note: Prices are averages for UK/EU/US markets

Walk outside and inspect the boiler flue terminal. Ensure it is not blocked by bird nests, leaves, snow, or debris. Blockages alter the pressure dynamics inside the boiler casing, though they more frequently cause a related fault where the switch fails to close . Step 3: Listen to the Boiler Startup Sequence

Review recent maintenance or changes

A: No. The boiler will safely shut down. It does not indicate a gas leak or carbon monoxide risk. But you will lose heating and hot water.

For a heat pump compressor to run safely, a minimum volumetric flow of water must constantly circulate through the secondary condenser circuit. If the flow rate drops below the built-in threshold, the internal paddle switch or flow sensor opens. The heat pump throws a D6 fault to prevent the refrigerant loop from overheating or freezing the heat exchanger. Common Causes of the Boiler D6 Fault (EA1 Module Input DE1) If the board is faulty, a full PCB

Locate the plastic pipe running from the bottom of your boiler to an outside drain.

If the pressure is fine and a reset doesn't work, the issue is likely internal. A Viessmann Trained Installer or Gas Safe engineer will need to: Installation Instructions - Flow Sensor - Viessmann US

Loose connections, corroded terminals, or a damaged wiring harness between the switch and the main circuit board can disrupt the electrical signals. The control board may misinterpret a short circuit as a closed pressure switch. 5. Main Control Board (PCB) Failure