QuestionI have a 74 Cutlass Supreme, I have been having some issues with the battery. I put in a new battery in the car and the battery went dead. I have charged the battery and after one night the battery was dead once again. What should I be looking for to prevent this from happening?
AnswerThere is nothing wrong with the battery, the problem is that something in the car is draining the battery. Some electrical item is staying on when you park the car. Usually this is something that has power all the time, even with the key off. Typically, this is a power seat motor, electric radio antenna, the light in the trunk, under the hood, or the glove box. Check all of those things to make sure they are not staying on all night, and if you can't find the problem, you'll have to do some detective work to find the problem.
Start out by taking one of the battery cables loose when you turn the car off, then tap the cable on the battery post to see if you can draw a spark. If you can, you now KNOW that something is on in the car. Next step is to start pulling fuses out of the fuse block, one at a time, rechecking for a spark as above each time you pull another fuse. If the spark goes away, the last fuse you pulled goes to whatever is causing the problem. From there, you have to look up what items are powered by that particular fuse, and disconnect those items, one by one, until the spark goes away even with the fuse installed. The last item disconnected when the spark goes away is the culprit.
If you go through all this and wind up with ALL the fuses pulled out, and still you see a spark, your problem is probably a bad diode in the alternator - disconnect the large wire from the alternator to see if that clears the problem.
Until you have tracked down the problem, you should always disconnect one battery cable every time you park the car, else you may lose the car due to fire. This will also prevent the battery running down overnight, so you can continue to use the car if you have to - just hook up the battery each morning - drive to where you have to go, and then disconnect it again when you park the car.
If the current drain is too small to cause a spark when you tap the cable end on the battery post, you will have to obtain a VOM (Volt-Ohm-Meter) and use it to measure the current drain. Since it is draining the battery overnight, it must be a fairly hefty drain, I'd guess at least 10 amperes, so make sure the meter can read that high.
By the way, whatever is staying on or causing the drain has to be getting quite hot - if it is the alternator, for instance, if you come back out to the car an hour or so after it is parked, the alternator will be too hot to touch.
Good luck - this is going to take some real detective work, but it can be done. If you take it to an auto-electric shop, they can find it quickly, but that will be very expensive - those guys are pros, and they don't work cheap!
Good Luck, you're going to need it!
Dick
