Cadillac Repair: Trouble with battery draining on a 90 Cadillac DeVille, cadillac deville, negative cable

Question
Hi Ed, I just recently bought a 1990 Cadillac DeVille from my uncle for a really good price since he could not figure out what was wrong with it. The problem is the battery will drain if you leave it hooked up for even just a few hours. I even had to get a boost the other day after I went into a store for a few hours. Me and my dad have checked for lights that might be on in the trunk, glove dept. and etc. The car has a battery on it that is pretty new. We figure it must be something pretty major to be draining the battery so quick so I was hoping you could help me out. Not much fun having to unhook the battery everytime you get out somewhere! Any advice you have will be greatly appreciated!

Thanks, Alex

Answer
Hi,Alex

You'll need to check for a draw,if you have access to a DVOM{Digital multimeter}then disconnect the neg battery cable,set the meter to amps scale,then connect the multimeter leads one lead to the battery negative side the other to the negative cable,it will show you how much of an amp draw you have,anything less than .025ma is ok,im sure you have way more,then you will need to pull fuses one at a time to see which ckt is causing a draw.
 Some things to check and are common with the 90 devilles,one is the level control compressor,it is located under in the engine compartment and on the left fender,usually the exhaust valve is stuck,though the compressor is not running it will cycle the exhaust valve,this causes a 1.5a to 2.0a draw enough to kill the battery,also radio amps,cig lighter sockets both the ft and rear,i have seen these shorted and cause a draw even without the elements in them.

ED