I've had half a dozen Garmin GPS's in my life....they have all turned on and off with the ignition. switch in my cars. Well, my newly purchased 3590 will not. It has a sleep feature and and off feature, but the only way I can get either to work is with the switch on the upper left corner of the unit. Can anyone tell me if I'm missing something, or is this just the nature of the beast? Any help would be appreciated!!! Thanks Ken