I bought a house with a Whirlpool WRB322DMBM00 bottom-freezer refrigerator. There was an ice maker installed, but to my knowledge never had water connected to it. I got copper tubing and connected it to a nearby cold water line. At first, I also added a reverse osmosis filter inline. The water pressure seemed fine (although I do not have the tools to check it).

No leaks when I turned on the water. After about an hour, it popped out a few ice cubes. Then a short while later I heard it start filling up. It never stopped. I read that the filters could lower the pressure enough to cause this, so I removed the filter and coupled the two ends together. Same thing. I took off the back plate, disconnected both water lines and the power to the valve and put it back together. Same thing.

Like I said, I don't have a pressure meter, but when I put the tube in the sink and turn it on, the water really blasts in there. It's hard to imagine pressure is the issue.

Before I buy a new valve, is there anything else I should try? It seems odd that a part never used before should be defective, but I'm sure stranger things have happened.

Sorry for the lengthy post, and thanks in advance for your help!