Hi, my name is Cleeve. I am the Service Manager at La Jolla Audio Repair in San Diego,Ca. The ML radio's are made by Panasonic just to let you know. The problem you have is a bit unusual. The first thing you should do is confirm that the Keyed +12 volt on the back of the radio is in fact turning off with the key. Since if it stays on for what ever reason the radio would not know to turn off. If it is turning off then the problem may very well be in the radio and should be serviced. Our repair facility can handle that for you. Please call me at (858)373-0596 for further help and service.