Thema "Betreff: B7 and 200-W" in Gas

B7 and 200-W

km1967 — Thu, 30 Jul 2026 17:10:37 GMT

hello

This is related to an old thread, see:

https://community.viessmann.de/t5/Gas/200-w-und-B7-und-pressure-druck/m-p/626377#M145748

The book given with boiler is marked Vitodens 200-W Typ B2HB / B2KB. The kessel number is 7570782...

At time of that thread I was able to clear the issue with a power reset and pressing "R", though it took a few tries.

Same issue came about a week later, that time just a single press of "R" fixed it.

It has happened 3rd time today and even with power cycle I have not been able to complete the reset successfully

The pressure issue on that other thread seems non-issue, gauge is where it was several weeks ago.

One common factor to all 3 issues is that this has happened on very hot days (ca: 35 deg C) here in Bavaria. But the boiler is in my cellar, which is pretty cool in caparison.

Boiler is ca: 6 years old.

Betreff: B7 and 200-W

divanc — Fri, 31 Jul 2026 09:00:35 GMT

Hello @km1967

Error B7 indicates a problem with the coding plug (part number 7863506, type 2A03:0203).
You can start by cleaning the contacts on the coding plug.
To do this, you need to turn off the main switch, remove the front cover and the boiler control unit cover, pull out the coding plug, and clean the contacts.
If this does not resolve the issue, the coding plug (order number 7863506) will need to be replaced.

If the system pressure continues to fluctuate, the expansion vessel should also be checked.

Best regards

Betreff: B7 and 200-W

km1967 — Fri, 31 Jul 2026 10:20:11 GMT

Thanks for help, advice, and clear instructions.

I was able to access to coding plug, see attachment, and cleaned both sides' contacts with a bit of alcohol

On power up I saw a progress bar, which was not there on other power ups. But after that disappeared shortly thereafterwards I got same B7 error. After acknowledging the error, I tried "R" again and this time it cleared, so boiler is currently up again.

What would you advise now?

Would the part you suggest not be replaced by Viessmann under the boiler warranty?

Would it not be wise to maybe get a replacement part now?

Betreff: B7 and 200-W

divanc — Fri, 31 Jul 2026 11:38:43 GMT

Hello @km1967

If it was merely an oxidized contact, the error will not recur; otherwise, the coding plug will need to be replaced.

I believe that, unfortunately, the warranty has expired after six years.

https://www.loebbeshop.de/7863506-viessmann-codierstecker-2a03-0203-fuer-vitodens-b2hb-2-4-19kw/

Best regards,