ᐅ Juncker gas boiler shuts off after ignition

Hello,
The gas boiler briefly shuts off after ignition. Then the temperature rises to 95°C (203°F), then drops to 65°C (149°F)... after that, it can no longer be ignited.

The safety valve has been replaced and water refilled.

Earlier, I heard a bang/rattling noise in the boiler.

Does anyone know this problem?

Does the device show no error code?

Grobmutant schrieb:

Does the device show any error code?

At first, EA appeared, then I noticed that the gas valve of both Juncker gas boilers was closed.
I opened it, and then it ignited. I heard a short bang after I turned one radiator to 5. Since then, it shuts off shortly after ignition.

Condensation is to be expected when the gas valve is turned off.
It’s strange that no other error is displayed.
But there is enough water, right?

Grobmutant schrieb:

Leak detection (EA) is expected when the gas valve is turned off.
Strange that no other error is displayed.
Is there enough water though?

Yes, there is enough water. As mentioned, it only shows initial values like p1 to p5, then 95, 65—I assume these are temperature readings.

Does it get a flame at all? I might only be sharing partial knowledge, but at least I can share my experience with our Vaillant gas condensing boiler. Over the past few months, I have had frequent misfires up to a complete failure. In the end, it turned out that the gas valve, which controls the gas mixture, was faulty. On top of that, the lambda sensor was slightly damaged and therefore could no longer correctly determine the mixture. I don’t know if this helps, but maybe check in this area?