Saeco Moltio error 15 with cappuccino reference

Hello all.
I have a Saeco Moltio the error code 15.
According to instructions I measured the two thermostats through
.
One was defective.
As a result I replaced that one and all was well again. I was able to pull a cafe, but as soon as the first cappuccino was pulled, the error was back.
Do I understand correctly that the "thermostats" are more like thermal fuses? As soon as the boiler gets too hot, the thermostats trip and turn off the heating?
The heater/boiler gets hot and has about 27 ohms.

I would now have the control board in the suspicion ...

Can someone say something about it and bring some light into the darkness?

Thanks and greetings

There could be a defect in the triac that controls the heating. But then it should also heat when it is not switched on.

Hello, thank you for the answer.
As soon as the machine is connected to the mains, it is heated. I could also observe that. Without the stand-by button being pressed.

Greetings

I would change the triac. Usually sits on a heat sink. Best to track with a multimeter so you have the right one.

All right. I'll have a look at the circuit board. Any other components to check in the process?
Thanks and greetings

Nope, first make sure the machine is running again.

So... thanks for the support. Today I removed the power board and replaced the triac. The old triac had 84 ohms between the outer two legs.
Soldered in the new one and now the heater switches off again.

Thanks again and greetings

Super that the machine is running again. Thanks for the feedback.