[Dougc]

I set the machine on "rinse and hold" as usual and left the house for an hour. Upon returning the floor was flooded and the machine was still running. I had to manually turn it off. Do you have any idea what is wrong? Is there a float system like a toilet that senses when it is full? Thank you, Doug C.

[denman]

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Replacement parts for GE GSD4020Z00BB | AppliancePartsPros.com

I set the machine on "rinse and hold" as usual and left the house for an hour. Upon returning the floor was flooded and the machine was still running. I had to manually turn it off. Do you have any idea what is wrong?
How did you turn it off?
If you opened the door or turned the unit to off and the water stopped then your timer must have stuck on fill.

Is there a float system like a toilet that senses when it is full?
You also have a problem with the flood switch (behind the kick plate left hand side). This switch is operated by the float in the tub. If the tub overfills the float rises and the switch underneath is supposed to open, shutting off the fill valve.

If you had to shut the water off to stop it, see the below link as the problem is the same as this. The valve is sticking open.
Kitchen Aid dishwasher filler valve stuck on