Heating on the 4450 goes off

After posting the problem I remebered that my mother used to use vinegar to desolve mineral resedeu from water containers and coffee machines. So I filled the heater well with some vinegar aqnd let it sit over night and it desolved the resedue. Under all that grit was actually metal and on a trial run the machine worked fine. So I'm pretty sure the problem is solved.

. goth_maiden, I have the same problem. Unit was my bf's and he never cleans anything so I can imagine the buildup. I can't make rice in a normal pot without it getting sticky or mushy so I wanted to try this steamer. I was trying to make rice and the unit shuts off after 1 minute - it would than go back on again but I had to either reset by pulling out plug (sometimes even that didn't work) or just remove the lid and move the unit around a bit. I am going to try the vinegar soaking method you mentioned and see if it fixes it. I don't know what the original color of the heating well is supposed to be but it now now it is like a light grey color. I will post again if this works. DId it work for you? Thanks!