I have a 2005 Mustang GT and earlier and noticed that my windows, door locks, and headlights were not working properly. I guess you could say the electrical system overall was acting sort of funny, actually as I took my key out the ignition and opened the door to leave the car the radio and lights inside stay on it was pretty weird. so I took it to AutoZone got the battery checked in the battery was bad so I figured that was a problem and had the battery replaced but still giving me the problems. Seems like an electrical issue has anyone ever had this or know what it might be causing it. Mechanics around here are no help and just offer a diagnostics test at $100 which is ridiculous. Any ideas?