Car battery was draining overnight in the cold. Couldn't start my car in winter if I left it sitting for 24 hours. The problem was the stereo, and it was very difficult to diagnose. I had to put a multimeter on the battery and pull one electrical component at a time. Pulling fuses didn't reveal the problem, I had to completely remove the stereo to reveal it. Overall, took several weeknights in the cold winter to diagnose, and another weeknight to replace the stereo.

Car kept dying. The problem was that the switch the the door presses to indicate it's open or closed got completely pushed into the door frame, which was draining the battery.

Every 9-12 months my battery drains without warning from my dashboard. I have gone thru six batteries since I have had the car brand new. I have had the clasps replaced. This keeps getting me stuck out in public with a non-working car. When I finally take it back to AutoZone, they replace the battery. But no one knows what keeps draining my battery.