What to Do if Your Alternator Dies While Driving

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Learn what to do if you lose vehicle power mid-journey
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The alternator is responsible for keeping your vehicle’s electrical systems charged after the battery has done its job starting the car. So, if your alternator goes out, you’ll slowly lose power until your car dies. With a drained battery, you won’t be able to start the car again—although jumping the battery will bring your vehicle back to life temporarily. In this article, we’ll break down why alternators die, what happens when they do, and what you should do about it.

What Happens if My Alternator Dies While Driving

If your alternator fails while you’re driving, you’ll lose electrical power in your vehicle. The car will die and you’ll be unable to start it again. However, if you jump the battery, you’ll be able to start the car again—just know it’s going to die again if the alternator is bad.

Section 1 of 6:

What happens if your alternator dies?

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  1. The car battery stores the charge needed to start the car, but once the car is started, its job is done. This is where the alternator comes in; it takes some of the rotational energy of your engine and converts it to electricity for your vehicle. So, if the alternator dies while you’re driving, your car will run out of electricity and die while you’re driving. You’ll likely notice something seems “off” with your interior lights or power steering before the car runs out of power. [1]
    • How fast your car dies out once the alternator dies depends on how much charge your battery has remaining. In most cases, it should be under 30-45 seconds between noticing something is off and your car’s power cutting out.
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Section 2 of 6:

What do you do next if your alternator dies while driving?

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  1. If you’re on the highway, pull off to the shoulder if you aren’t near an exit. Above all, don’t freak out—now is not the time for sudden movements. Honk or throw your hazards on if there’s traffic between you and the nearest shoulder, parking lot, or parking space. [2]
    • What if it’s hard to steer? Your power steering system needs electricity, so it will become progressively harder to steer if your alternator goes out. Don’t give up—use enough force to turn the wheel and steer the car to safety. You will not do more damage by steering harder than normal.
Section 3 of 6:

Can you jump a car with a bad alternator?

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  1. The alternator actually isn’t responsible for starting the car—your battery is. The alternator just keeps the battery charging while the car is running. So, you can definitely jump the battery to get the car started, just don’t expect the car to stay on for very long if the alternator is bad.
    • What does it mean if your car doesn’t die after you jump it? This is a huge diagnostic sign that your alternator is actually fine— your battery is probably to blame . The alternator’s only job is to keep the electrical on after the car starts, so if it’s doing that it’s unlikely to be the issue.
    • Can you keep jumping a car with a bad alternator? If you aren’t far from the mechanic, traffic isn’t crazy, and you can safely jump your car, drive a bit, then pull over and do it again, go for it.
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Section 4 of 6:

Can you drive with a bad alternator?

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  1. You aren’t going to do any serious damage to your vehicle if you drive with an alternator that’s slowly dying. However, you shouldn’t tempt fate if you aren’t confident that the car will actually stay on and you have to drive any kind of serious distance (or through heavy traffic).
    • You’re probably going to have to jump the car every time it dies, just FYI. You won’t be able to drive, stop, and drive again without a friend tailing you to jump the battery.
    • If your car’s power isn’t cutting out immediately and you can spot when the power is starting to drain and prepare to pull over, it’ll help you finish the trip a lot more safely. Just monitor the brightness of your interior lights. When they start to dim, pull over.
Section 5 of 6:

Signs of a Bad Alternator

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  1. A bad alternator will not prevent your car from starting. However, you will start to lose power as the alternator dies. Your cabin lights will start to go out, your headlights will dim, and anything that requires electricity will start to malfunction or die. [3] Other signs your alternator is bad include:
    • Growling or whirling noises in your engine bay. The alternator wraps around a length of your serpentine belt (aka timing belt). If the alternator isn’t rotating, it will grind against the belt and cause friction and noise.
    • Burning rubber smells. As the timing belt grinds against the alternator, the friction will start to heat the belt up. This can cause a burnt rubber aroma in the cabin of the car.
    • Low voltage readings. If you have a battery gauge, look at the dial. If the voltage indicator slowly goes down or bounces around while you drive, your alternator is probably bad.
    • Error lights on the dashboard. If you have a dedicated alternator dash light, it’ll pop on. If you don’t, the check engine or battery voltage error lights will likely illuminate.
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Section 6 of 6:

What causes an alternator to fail?

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  1. Your alternator may fail if you have a blown fuse or your car has run into some major electrical failures, but alternators normally fail due to mundane wear and tear. Expect an alternator to last around 100,000 miles (160,000 km) or so, although your alternator may not last as long if you live in an especially harsh climate. [4]
    • How do I fix my alternator? This is a professional repair. See a mechanic to have them install a new alternator. If the serpentine belt simply snapped, you can try replacing it on your own to see if that solves the problem.
    • How much does it cost to replace an alternator? Expect to spend $750-850 on a new alternator.

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      References

      1. ↑ https://www.aaa.com/autorepair/articles/bad-alternator-vs-bad-battery
      2. ↑ https://www.aaa.com/autorepair/articles/bad-alternator-vs-bad-battery
      3. ↑ https://www.kbb.com/service-repair-guide/alternator-replacement-costs/
      4. ↑ https://www.kbb.com/service-repair-guide/alternator-replacement-costs/

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