Cadillac Repair: 1998 Cadillac Sedan Deville battery runs down over night, cadillac sedan deville, air lines

Question
Dear Autohelp, my mother-in-law has a 1998 Cadillac Sedan Deville. It's a really nice car but for some reason the battery keeps going dead overnight. She's taken it to a couple of mechanics to fix the problem, but they can't seem to figure out what's wrong, and she's out the money for their time. I tried to find a web site for answers, but can only find one's that offer a manual ( which is always very general in the fix-it department ). Could you give me a few areas to look for (sort of trouble shoot the problem), and maybe I can help her out. She's a very dear person who will do anything for anyone, and she's getting very desperate. Thank you for your attention and effort in this matter. Warren Brown

Answer
The most likely fault is either a failure in the HEIGHT SENSOR or a leak in one of the air lines which will cause the compressor to run periodically during the night thus draining the battery.

Look to see if the rear end of the car is much lower than usual in the mornings.