How far can you drive on a bad alternator?

75 - 80 miles sounds pretty good. If your alternator crapped out it might be cheaper to buy a battery and charge the one in the car to get home, depending on the distance, and then install the spare alternator once you got the car home. Might save a tow charge if your stuck on the side of a highway.

How much is a battery alternator?

In some models, they can run as low as $180 and for premium vehicles, they can run over $1,000. The average cost is approximately $500. It is common that the alternator will fail due to worn out contact rings and carbon brushes, or problems with voltage regulator.

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