So my Mustang was sitting for about five days before I went to drive it the other day and the battery was dead. I figured it was just due to my Ipod charger being left in the outlet. A friend jumped me and I drove a little while. Then earlier today I went out to go somewhere and it was dead again. I have no idea what the problem could be, because nothing was left plugged into the outlet, my lights were off and the dome light was also turned off. I had heard of some people with 1999's having trouble with the door sensor malfunctioning causing the dome light to stay on, but mine has been turning off. Does anyone have any input on what the problem could be? When I tried starting it, it didn't turn over at all; nothing happened at all when I turned the key.