Sounds like something is drawing current w/ sw turned off. Alternator can have a bad diode & still charge when it is running, but when you turn engine off, it will pull juice back out of your battery. This can be detected either by using a professional tester, or by taking the negative cable off & touching it to the terminal to see if you draw a spark. This actually works better if it is a little dark when you do it. If you see a spark, then something is definitely drawing current. Everything in the car should be off, including ign switch to do this. If there is a spark, then try pulling all the fuses & trying this again. If no spark w/ fuses pulled, put them back one at a time & repeat spark test. (You can use an amp meter for this if available) If you get a spark after installing a paticular fuse, then you have found your draw. If it does it with all fuses out, it is probably the alternator, or a grounded wire somewhere. Ovmf