Not sure if this will help, but the trunk pin switch for the trunk light can break and keep the bulb on but I would think it would take longer than overnight to drain a battery with just that little bulb.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U