Here's an old trick from my car fixin days: Pull the positive battery cable and hook a test light (12v voltage indicator) between the battery and the positive battery cable. Start pulling and replacing fuses until the light goes out. When you isolate the circuit, put the fuse back in and begin disconnecting components or cable connections to isolate the source of the drain. It is the same as Larry's ammeter, only the light has the advantage of being easily seen from where ever you are in the car. Helps when you are under the dash or in the trunk and have to look up. Good luck!