1998 Cadillac Sedan Deville battery runs down over night

Answer 1

This may sound stupid, but it happened to my Father on his 1993 deVille.  His 80+ year old girlfriend would pick up change, mostly pennies, off of the floor and drop them in the ash tray.  The problem arose because my Son had removed the ciger lighter to charge a phone or something similar and a penny or two got into the lighter socket.  When the lighter was placed back into the receptacle, it was as if it was pushed in , even though it was just sitting on the penny.  It eventually melted the wiring harness, which had to be replaced.  Maybe this will help.  I had tried removing all of the courtesy lights under the hood and in the trunk and replaced the battery 5 or 6 times before finding the problem.  Good luck!