04 Chevy Classic. Fully charged new battery drains overnight. I disconnected the negative battery cable and connected a test light to the cable and to the negative side of the battery. I get a strong light on the test light - I checked connection from the battery both posts to the engine block and starter motor. Checked doom light is out. No door lights, parking lights, brake lights. Tested brake light switch. Reset/pulled all fuses and resistors etc in fuse box - all connections are clean - test light stayed on entire time. Assuming a wire somewhere in the car may be grounding against the body. Bad alternator, bad starter motor, window motor? Any advise on a process to find what is draining the battery.

Thanks,

Milty