So as I am rebuilding it, an idea pop up in my mind.
I have heard that in HX E61 machines, sometimes we may get the water filling kicking in in the middle of a shot.
To prevent that, can I add two wires to the machine:
one wire connecting one terminal of the brew switch to the water level probe
one wire connecting the other terminal of the brew switch to the boiler

That way when the brew switch is activated, it would close the circuit of the water level detecting function, and thus not activate the auto fill?
Of course, risk is that if someone start opening the hot water tap and let the boiler drain during a pull, it would expose the heating element and damage it....

What is your thought? Would it work?

Answer my question... it wont work...
the microswitch for brewing runs at 110V... If I connect that in parallel to the water probe, I will fry something or electrocute myself.

Follow up:
E61 HX machines are such a joy to make coffee with! Pulled over 40 shots in the past week. It definitely runs hot as I leave it on during working hours. Takes like a 10-20 second flush before the flash boiling stops in the group.

Another question:
Since there is only one port on the group, is it more useful to put a thermometer or pressure gauge there?

baldheadracing wrote:Looks like a pressure regulator. .

Yes. I had a Millenium decades ago and played with lots of plumbing options. I had a pressure regulator that looked almost exactly like that except I had mine on the actual water supply line feeding the machine. It was incredibly cheap and went in the trash after a month.

strikeraj wrote: Another question:
Since there is only one port on the group, is it more useful to put a thermometer or pressure gauge there?

I don't own an HX, but have been looking into this topic recently.

For HX, it seems that temperature is more useful because of the temperature regulation that needs to be done. Once people have a feel for the machine and managing its temperature, I read that some switch to a pressure gauge.

If you're ever going to look into flow control, you'll be getting a pressure gauge in those kits anyway. So if you buy a pressure gauge now, you'll end up with a 2nd.

Aside: do any stores sell just the needle valve alone?

Glad the machine is working well and you're enjoying your shots!