Take an ear bulb/syringe and put it on the level tube while it is still attached to the barometric (water level) switch…you could alternatively blow up the tube with your mouth…while the machine fills with water,…blow into the water level tube…if it doesn’t turn the water off then the problem is further up the water level mechanism…
Take a wire and while the machine fills with water “jump” the two leads that go to barometric switch together…if the water stops the problem is the barometric switch…if it keeps filling the problem is further up the mechanism…
trace the leads to where they go…it will be somewhere near the controls at the top of machine…check to see if the wires are connected and wires are unbroken…if they are then the problem is in the timer/control mechanism and should be replaced.
Sounds like a solenoid is hung open, probably has crap stuck in it. Disassemble it and clean it out.
This is a very good idea...Does the water turn off and on when you turn the machine on and off?