Going through batteries? Check your alternator.

Dear Car Talk

Dear Car Talk | Feb 01, 1996

Dear Tom and Ray:

17 months after we purchased our 1990 Ford T-bird, the original 60-month battery died (with no warning signs) and had to be replaced. 19 months later, THAT 60-month battery died (again, without warning) and had to be replaced. 18 months later, the "low battery" indicator light came on and stayed on while driving. This time, we were told that a diode was bad in the alternator. We had it replaced at a cost of $240. All three times, we took the car to the Ford dealer, and only the last time were they able to find a charging problem. Is it possible that the alternator was defective all along and that it caused both batteries to go dead? And if that's the case, shouldn't the Ford dealer cheerfully refund my money for the batteries?

TOM: It is possible that the alternator was under-charging from the very beginning, Carol.

RAY: Something WE'VE never been accused of doing at OUR garage, I might add.

TOM: The alternator may not have been performing badly enough to kick on the "battery" light until the very end. It was obviously working to some extent, because it kept each battery going for a year and a half. But if it were under-charging by just a little bit, that would explain why your batteries died early deaths.

RAY: A weak or failing alternator would be the first thing I'd suspect if someone came in with a dead battery. So I'd be surprised if the Ford dealer didn't check the alternator each time. But it IS possible that they didn't check it correctly. A lot of garages are guilty of just checking the voltage and not checking the amperage output. And when there's any question about the alternator, it's always important to check both.

RAY: In either case, it's going to be almost impossible to prove negligence at this point, Carol. So I doubt they'll be refunding your money, cheerfully or otherwise. If I were you, I'd just consider it battery acid under the bridge.

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