You need to give the year and mileage of your car. It is a well known fact that the Bose stereo causes a brand new battery to drain overnight for 2003, 2004 models. I encountered this problem over a year ago. I replaced the battery, it was drained overnight. Did a search, the culprit was the Bose stereo. Replace the Bose head unit with a Pioneer and replacee the heating/AC control unit on the dash. Because the heating/AC is part the Bose control unit. After that, all was well.

Hate that Bose unit!

 

There is a simple way to troubleshoot the Bose leak. Pull out the radio fuse the night before and see whether the car starts in the morning. If the car starts, then you know it's the Bose. Order the parts you need so you can replace the Bose control unit and still be able to drive the car without the radio fuse. The heating/AC control unit will go to default but still workable, you cannot make adjustment to it without the fuse. Any car radio shop can replace the radio and the heating/AC control unit, but you have to order the control unit yourself. You can do a search online to order that.