I have tried to get some type of logic thread of the use of a low water sensor on the Lusso....double safety in combination with the thermostat cutoff switch I suppose or perhaps a feature that looks good on paper. This format machine existed for a very long time with a simple switch-pstat-element-pilot light circuit with not a lot of problems. The thermostat was added to control for runaway heating and this was a very simple solution that could be wired into the existing circuit easily. It seems to me that the brain is not sophisticated enough to read the varying resistances that come through the low water probe and the water in the boiler as mineral content of the water would throw it off, or at least be inconsistent. As an experiment, take the probes of a multimeter set on ohms and put them in a vessel of water and watch what happens....pretty wild resistance readings and the brain is supposed to sort out these readings? Seems a difficult task for such a simple brain. The pre brain/low water sensor models are much more stable or at least simple, and seemingly just as safe.

So to remove the black knobs, I have to unscrew the brass bits to unloose the total stem.
I wrote the dealer (in Italy). They can do 2 things, or I send back the PV and they will repair it (warranty), but I have to pay both ways of transport. Or they send the piece to replace the brain.

If I do it myself (assuming I get of the both valves), I can also insulate the boiler a bit, at least where the brain is situated. Sending it back and forward is easier, but will cost some euro (I assume about 30 euros one way).

I will try tonight if I can get off one of the stems on which the valves are positioned. If I will succeed, I will do it myself otherwise I will send it back.

I first have buy some lube too.