Car Talk: Sometimes you just lose your spark for unglamorous reasons

Dear Car Talk:

Recently I drove up to Pike’s Peak in Colorado (14,000-foot elevation). On the way down, I had my car in D3, 2, or 1, depending on how steep the grade was. Part way down, an attendant was stopping people to check their brakes. He said I was doing fine.

The following day, I drove 75 miles to Denver, and the car ran perfectly. But the day after that, I noticed an unusual noise when idling. I drove maybe 10 miles that day. The following day, I drove one block, and the battery light came on.

I drove back home and put the battery charger on the battery, and later went to drive it. It went 50 feet and died. It was towed to my mechanic, and he determined that I needed a new alternator. Do you think my problem was caused by the trip down Pike’s Peak? — Faye

In a word? No. My great uncle died that same week, and I don’t think we can blame that on your trip down Pike’s Peak either, Faye. The failure of the alternator can be blamed on the age of your car.

You don’t say how old the car is, but if it’s got 80,000-100,000 miles or more on it, your alternator is susceptible to failure. The alternator gets a ton of use. Every time you run the car, the alternator is spinning.

When it’s spinning, it’s pumping out electricity, which is used to power the car’s electrical systems and to recharge the battery. Once the alternator starts to fail, your battery will stop getting charged — or will get charged much more slowly than it needs to be.

That explains the low battery warning light, Faye. The battery will then continue to drain until, eventually, it gets so weak that it can’t provide enough power to energize the spark plugs. No spark, no go. So, the car stalls. And once the battery is that weak, you can’t restart the car, either.

And that’s what happened to you, Faye. Yours is a fairly typical presentation, where you hear some increased noise, see the battery or charging light come on, and then — kaput. But I do believe it kaputted of natural causes, Faye.

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