Classic/Antique Car Repair: Electrical ground, chev blazer, volt ohm meter

Question
99 Chev Blazer. Battery runs down overnight. Something causes large spark when terminals are connected on battery. Battery is relatively new. Battery holds charge when unhooked overnight. When a test light is connected between un-hooked black cable and battery terminal, it lights up. All fuses inside have been removed individually and the hot terminal removed from the outside fuse box with no resulting test light out. Hot wire and plug removed from alternator also. What else could be the shorted problem?
Thank you for your help,
Ken

Answer
The test light does not work on a vehicle with a computer as a test for drain. The computer stays alive al the time and is a drain of less than an amp on the battery all the time. The procedure is to use a digital volt ohm meter that also measure amps. Most of these meters will measure up to 10 amps. Place the meter in series with the disconnected battery cable and read the amp draw. Less than one amp is ok but more than one amp, start taking out fuses until you hit the circuit that lowers the reading. If you do not find it then let me know and we will go to step two.
Brad