No worries Eric
I wasn't trying to put anybody down

Yep, on my millennium the "Water tank switch" cuts the power completely. So it sounds like something else is at fault.

I was also noticing on my millenium, that either the green or red boiler status light is always on. So if there are periods where neither is on, I would suspect the heating element, pressurestat or something in that circuit?

If I remember correctly, it has been many years since I had my Millenium, when the water tank goes empty all three of the lights flash at you. Power light will always be on, heating light will be on for probably 15min while the system heats to its pressurestat set point then click off.

Sounds electrical like a bad brain box or SSR. The heater SSR sits on the bottom of the case, little white or ghost gray box if I remember correctly. There is a thermal fuse but if it were blown, it would not heat at all. On my machine the SSR was not screwed down. Just some thermal grease under it then pushed onto the case base. There was a thread a few years ago with the same issue on another machine. It would heat, die, cool down, heat, die, cool down. Do not remember what the fix was but a bad brain box sounds familiar.

The water tank is not the problem, as stefano said, the machine would have been off entirely.

Now, I spent $200 to have it "fixed" with a new heating element and that didn't do any good.
I confirm that the after a few minutes of operation only the power ligh stays on and the pressure goes down and there is no activity (on-off boiler heating).
As now, do you think is it even worth it to try to have it fixed?
The repair person seems like is trying to avoid me.

Like I mention before focus on the Relay inside the box
the external relay
and also the pressurestat
you will need a multimeter if you are confident or ask your repair person what they tested etc etc

If, when the machine powers down, the autofill also fails (check by removing the probe wire), the box is gone. The transformer is getting hot and as the resistance increases due to the heat, the voltage drops and the machine goes down. When the machine cools it comes back to life.

You can drill a few ventilation holes in the box to see if it helps. Not kidding.

If the autofill works but the machine gets cold, likely a bad coil on the relay. If everything else works okay, hot wire the relay so that it no longer gets power from the box. Most machine don't, no problem.

Thank you for the reply.

The first scenario you described is possible because the machine comes back to life after it cools down, and the refill works, until it gets hot again.

Unfortunately I don't have knowledge in all this and I don't even know what's the probe and box are.

I am debating whether it's worth to find another repair person and spend money to fix it.
I wish I could do it my self thou.

Thanks agin for help.

well,
the mention parts are easy to replace,
shoot and miss if you cannot diagnose the problem
from what you that you describe my feeling is that
the faulty component
is the relay inside the brainbox that get's sticky and stock open and once cools down works again,
but could also be the external relay as well,

the control box
is the most expensive part and I'M not trying to have you buying it just to buy it,
we have all the parts on our web page BUT none of electric parts are returnable.
OR take it to a QUALIFY repair center
good luck
Stefano

How about removing the external sheet metal and taking some pics of the inside of the machine?

I kinda doubt there is any relay in the control box other than the one that gets triggered on an autofill. But, quite possibly, you may have the Isomac exception. TYPICALLY, these machines (Isomac) have a solid state relay (SSR) which is mounted on the base (floor) of the machine. That SSR sends power (or not) to the heating element and is itself controlled by the pstat.

Eric perhaps the name of the component is wrong but there is device in there that does
activate power to the heating circuit
pin 5