I have a through-the-wall air conditioner, 220V, digital settings.

It started misbehaving when I tried to turn it off (by pressing the big red ON/OFF button).

The compressor still runs even though the display indicates that the unit is off.

I pulled the plug immediately--naturally, that shut the compressor. I left the unit unplugged for a few hours and tried again with the same results.

Any ideas as to what is wrong with the thing?

From the little I know about this stuff, if that compressor runs and the rest of the unit doesn't, the compressor will burn out...