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My Viessmann Vitodens 333-F does not start the gas burner automatically. Here is what I checked so far after logging in with viservice for the service menu and viexpert for the parameter Level 2 menu.

  • Boiler Temperature currently=20 °C set=5 °C Curve: slope=1.2 offset=6 K
  • Errorlog: Error B1 occured 3 months ago for the last time. The bug is currently not present any more. The error code addresses a contact problem with the display panel. Probably there was a bad contact to the panel or some bug.
  • There is no current Error. I even read out the controller in the service menu which reports 38:0 (=no error in the burner controller)
  • The pump is working
  • All temperature sensors are working fine and provide exact values.
  • I can switch the gas burner manually to base load in the service menu and it works fine as long as I am in this menu.

What I tried to force a change of the internal set=5 °C value, which is obviously wrong:

  • Temperature changes by the user
  • Power off/wait/on
  • Switching from heating + water boiler mode to water boiler mode. Ask for 42 °C water, water temperature reads 16°C, but the burner is not activated

There are other users who reported about the same problem, but there was no answer:

The hardware seems to be fine. How can I reset the controller so that it updates the set temperature again?

2 Answers 2

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If 33 is found at address 38, normally it is an indication for an internal fault.

If 0 is found at address 38, still the problem could be caused by a bad capacitor.

The control circuit board of this Viessmann system is known for bad electrolytic capacitors. In over 90% of all Viessmann 333 problems, strange defects and/or missing error codes, the anomalies will disappear after replacing those capacitors.

Often the electrolytic fluid has leaked and/or the capacitor's case is torn or bulged.

See the many hints for this specific capacitor problem in the internet. Millions of those faulty capacitors were produced and used in electronic devices 10-25 years ago.

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  • This seems quite reasonable. Do you have a pointer on how to fix it? Is it a matter of desoldering the caps from the board? Does it require replacing the whole board? I know this is over and above the question asked, but it would be helpful info.
    – FreeMan
    Commented Feb 23, 2022 at 13:41
  • @FreeMan, Yes, the capacitor needs to be replaced then. Selecting a proper replacement can be trivial or tricky depending on the position in the circuit, because a cap is more than a single capacity with a max voltage rating. If unsure ask on electronics.sx Commented Feb 23, 2022 at 19:07
  • thanks, @JonasStein, and BTW [electronics.se] will automatically be expanded to Electrical Engineering. ;)
    – FreeMan
    Commented Feb 23, 2022 at 19:11
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The heating could be reactivated by setting the tap water temperature to 10 °C. The tap water was cold then of course, but the heating started working again.

Then we exchanged the NTC boiler temperature sensor Part-no. 7819967. The sensor was a little corroded, but the R value for 10 °C and 20 °C were perfect.

However after changing the sensor the heating and the warm water boiler were 100% functional again. I was surprised, that the controller was not able to detect this fault, but reacted with extreme malfunction. The temperature readings in the controller were fine too. Hence I did not expect a broken NTC. Probably there was just a problem with the insulation of the NTC, or the software was in a loop which was cancelled by exchanging the sensor.

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