What could be causing this battery to lose its charge?

Dear Car Talk

Dear Car Talk | Jun 01, 1995

Dear Tom and Ray:

Boy, do I hope you can answer my question! We have a 1973 Chevy Open Road Van that keeps wearing down the battery. We have had the camper to two different vehicle electrical shops and they told us all we needed was a new battery. We replaced the battery (and, incidentally, the alternator) and it still runs the battery down after about two or three days. We don't drive the camper very much and it does sit in the driveway for a week at a time without use. Can you suggest what else we can have checked? It sure is frustrating to keep being told that all we need is a new battery.

RAY: All you need is a new battery, Cathy. Just kidding.

TOM: Think of current like CurrenCY, Cathy. If you have a shortfall, it's either because there's too much going out, or not enough coming in.

RAY: Or, like my brother, you have an ex-wife with a serious Bloomingdales habit.

TOM: Let's take the issue of too much going out. That's often caused by a current drain. Something may be draining current from the battery while the car isn't even running; while it's just parked, collecting tree sap in your front yard.

RAY: Your mechanic can check for that very easily with an ammeter. Or, you can do it yourself by just disconnecting the battery whenever you leave the camper parked for a while. If the problem goes away, you know that something WAS draining the battery.

TOM: The other possibility is that your not PRODUCING enough current to charge the battery. The alternator is supposed to charge the battery when you drive the car. And even though you replaced the alternator, it may be the wrong alternator. Or, you may have added so many accessories to the van that the alternator is no longer sufficient. It might just be that the alternator belt is loose and slipping, or the alternator belt may be driven by ANOTHER device, whose belt it loose. There are a number of ways the alternator could be at fault.

RAY: It's too bad the mechanics you went to weren't more interested. Electrical problems can be hard to find, so you're going to have to find a mechanic who's really willing to work with you, Cathy.

TOM: Here's what I'd do. I'd go to the bank, give the loan officer 20 bucks, and ask him for the name of a local mechanic who's falling behind on his boat payments. I'm sure that guy will be willing to spend as many hours as are required to track down your problem. Good luck.

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