You could replace the battery and and test with voltmeter all day long , but unless you know where the current draw is you'll never fix it. If there is a draw anywhere in the system all the volt readings will show normal, What you need is OHM(resistance) checks for continuity to ground where it shouldn't be. You need to disconnect every component from the wiring harness, and check them for continuity to ground. If you isolate them and they all check out OK, then you need to disconnect all the ground attachment points of the harness to the frame. and check for continuity of the harness to the frame remember to check all wires including the negative side leads. If it was a positive lead you'd have a blown fuse. Send me a PM if you need help. I can help walk you through it..