Programming or re-addressing a Vaillant PCB (Printed Circuit Board) is sometimes necessary after replacing a board on older Vaillant ecoTEC boilers, particularly units manufactured before 2015. These models use a manual parameter-entry system, which means the engineer must select the correct boiler code to ensure safe and efficient operation.

Below is a clear, engineer-focused guide explaining how to access diagnostic mode, enter DSN (Device Serial Number) settings, and program the correct model type.

When Do You Need to Program the PCB?

You will usually need to program or reprogram a Vaillant PCB when:

• A new or refurbished PCB has been installed
• The boiler is displaying the F.70 fault code (model mismatch)
• The boiler is operating incorrectly after a board change
• Components such as the gas valve or fan are not modulating correctly
• Hot water or heating output is incorrect due to wrong model identification

The F.70 error is the main symptom of an unconfigured or incorrectly programmed PCB.

Step-by-Step Guide: Programming Vaillant PCB (Pre-2015 Models)

1. Start With Error F.70 (If Displayed)

If the display shows F.70, this confirms the PCB is unprogrammed.
Press and hold the two right-hand buttons together to enter diagnostic mode.

2. Enter the Diagnosis Menu – d.0

Use the arrow buttons to navigate to d.0, then press OK to access the menu.

3. Navigate to Parameter d.97

Scroll until you reach d.97 – this parameter allows access to the DSN offset table.

4. Enter DSN Mode

Press and hold the two buttons indicated in Vaillant’s diagram for 5 seconds.
The display will flash and enter DSN mode.

5. DSN Offset Screen (XX = 0–99)

You will now see a two-digit number (XX) representing the model code.
This is where you select the correct boiler type.

6. Select the Correct Model Code

Use + / – to adjust the value according to the model table for your boiler.
Hold OK for 5 seconds to save.

7. Confirmation Code – d.93

The screen will display d.93, confirming that the selected model code is stored.

8. Reboot the Boiler and Check Temperatures

Return to the home screen and ensure the boiler displays temperatures normally.
Your PCB is now successfully programmed.

Pro Tips for Engineers

• Always confirm the boiler model using the rating plate before programming
• Check gas settings and modulating components after programming
• If F.70 remains, the PCB may be faulty or the wrong revision for the boiler
• Pre-2015 Vaillant PCBs do not auto-recognise the boiler type — manual entry is essential

Professional Vaillant PCB Programming & Diagnostics

At Certificates4UK Ltd, we specialise in Vaillant PCB programming, board replacements, and advanced diagnostics across:

• West Molesey
• Kingston
• Richmond
• Wimbledon
• Surrey & London

If your Vaillant boiler displays F.70, misfires, or refuses to operate after a board change, our engineers can program and test it correctly.

Link for support: Vaillant F.70 Fault Code – Invalid Device Specific Number (DSN) — Explains the F.70 error meaning and programming requirements.