This is a possible solution! On www.fixya.com they said to do this if anyone else has had this problem---it is worth checking out to fix an expensive cleaning machine!

There's a thermal fuse inside. If it gets too hot, the fuse will blow and the thing won't turn on.
It has a 216 C temp limit. You can find thermal fuses at radio shack for less than 5$. If you're adventurous enough, you can find the fuse in line of a white wire under a fiberglass outer and heat shrink inner shielding screwed against the bottom of the tank.