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What To Do If Your Alternator Goes Out


If your alternator goes out – your car isn’t going anywhere fast. Because your alternator charges your car’s battery, without it, you won’t be able to start your car, which means you’ll need a tow to the mechanic.

When you have a dead alternator, your battery will also die during normal use. Unfortunately, most people find out about their blown alternator because their car won’t start.

If you’re like most people in this situation, you’ll naturally want to jump your car battery.

But, if your alternator is busted, your battery won’t charge when the car is actually running – which will lead to, guess what?

A dead battery again.

That’s no fun.

But first, before you consider jumping your battery again (or doing what many people end up doing, and then getting a new battery) let’s figure out if your alternator really is busted.

What Does Your Alternator Do?

If you think about it, your car needs a lot of electricity. Most of us take for granted our headlights, dash lights, charging ports and the like, not to mention the engine starting. While it’s easy to assume the battery is providing this power and be done with it, that’s not entirely the truth.

While car batteries can have an enormous capacity compared to your iPhone, they need to be charged too, which is exactly what the alternator does. Your alternator translates mechanical energy (movement) into potential energy that’s stored in your battery via a spinning pulley.

This energy makes sure your battery is always full and always has the energy to start your car and run your nav, heater, stereo and the like.

Without a working alternator, you’re going to have a dead battery and a stalled car, which no one wants. The thing is, it can sometimes be difficult to tell the difference between a bad battery and a bad alternator, so let’s work our way through that first.

The Risks Of Driving With A Bad Alternator

There are a number of risks that driving with a bad alternator can pose. To clarify, a bad alternator is any alternator that isn’t charging the battery fully. The average car battery is a 12 volt, while most alternators produce over 14 volts in order to make sure your battery stays charged.

That’s because all of the electronic systems on your car rely on your battery to run. Without that battery being charged, you’re dead in the water.

A Bad Alternator Can Drain Your Battery At Best, And Destroy It At Worst

A bad alternator will result in a discharged (dead) battery and cause a vehicle to not start or run.

Alternators are designed to maintain a battery’s charge, not to recharge a dead battery. Your alternator’s job is to maintain a consistent charge on your battery.

Draining your car’s battery is not advised. Having it happen once won’t kill you. The more you do it, however, the worse your battery will perform. This can include destroying the battery completely through irreversible sulfation. If you want to learn more about the science behind this process, read this excellent Looper article.

On Newer Vehicles It Can Even Cause Damage To Your Engine

The reason newer cars present an even greater danger when the alternator fails is that there are cars with electric water pumps. If your water pump fails and the car miraculously keeps going, you will overheat and risk doing serious, permanent engine damage. The power steering in some cars is electrically driven.

Steering can be a real workout without that boost provided by the power steering pump. The fuel pumps on new cars are electric too. If the fuel pump stops, so does the motor. Of course, the same goes for the ignition. No spark, no go-go. If you have power steering, even the old fashioned belt-driven type, when the engine stops, the steering will suddenly become very stiff.

A non-running engine will also not provide a power brake booster with what it needs to help stop the car you’re suddenly having trouble steering. That’s a really bad combination.

A Worst Case Scenario Could Include You Losing Control While Driving

As mentioned above, considering how your power steering is linked to a working battery, if your car runs out of juice while driving, as you might guess, it’s probably not going to end well.

Here’s How To Know If Its The Battery Or Is It The Alternator

It’s easy to get the battery and the alternator confused. Together they both work to drive your car forward, albeit in different ways. It can be hard to tell the difference so let’s take a quick look at the symptoms of each.

One thing to keep in mind, your battery can go dead because of a blown alternator. The alternator is responsible for charging the battery, after all. If your alternator dies, the battery will die too. That doesn’t mean you have a bad battery, however.

The Signs That It’s Your Battery

Generally speaking, whenever someone comes into my shop and tells me the alternator on their car is dead, I’m a bit skeptical.

The average car battery is only rated to last between 3-5 years, whereas the alternator is rated to last for somewhere between 7-10 years (or 80,000-150,000 miles, depending on the driving conditions).

If you’re still trying to figure out if it’s your alternator or your battery, I’m fairly confident in saying it’s probably your battery, but it’s still worth checking.

1: Dim Headlights

Your car’s battery is responsible for powering your car’s electrical components, including your headlights. One of the first indicators that your battery is going out is weak headlights. If you notice one night that it’s harder to see than normal, pay attention. This is often a tell that your battery is on the out.

2: Trouble Starting The Car (And The Dreaded Clicking Sound When Turning The Key)

As your battery gets closer to the end of its lifetime, it’ll struggle to send current to the starter solenoid which is responsible for kickstarting your car. Because the battery struggles to send current, you’ll hear the starter recieving insuffient current, which is the dreaded clicking sound.

3: Slow Engine Crank

Is your engine cranking slower than usual all of a sudden? If you notice your engine isn’t jumping to start as quickly as you’d like, take note, because your battery is probably on the way out.

4: Battery Warning Light

Duh. I don’t think I need to explain this one any further. Those damn lights are there for a reason!

5: Your Battery Is F***ing Old!

“But it was working fine just yesterday!”

Sorry Karen, no it wasn’t. That battery was old, and it was about to bite it.

The standard car battery is designed to last between 3-5 years, and it can last even less in harsh conditions. If you can’t quite remember the last time your battery was changed, it may be worth checking in on it.

The Signs It’s Your Alternator

The one you really need to look out for is dim lights – not just your headlights at night, but your dash lights and nav lights. Pay attention at night and see if your lights are dim. If they are, do they flicker? Flickering lights are one of the telltale signs that your alternator is about to bite it.

Once you see your lights either dimming or flickering, accelerate a little bit and pay attention to if the light brightens. If it brightens at higher acceleration, I would personally recommend that you take your car into a mechanic if possible, because that’s about as sure of a sign as you’re going to get. But it’s not the only one.

1: Check Engine Light

A check engine light could be a number of things, but when your alternator decides to go, it can flash your battery light or your check engine light.

2: Grinding Noises

Inside of your alternator, there are a number of internal gears and bearings. As these wear out with age, they can cause a grinding sound that sounds like grain being milled.

3: Electrical Issues

Try your power seats or mirrors. If they are slow to operate – or stop working entirely, there’s an issue with your electrical system which may have a root cause with a busted alternator.

4: Stalled Engine

If your engine stalls when driving, there’s a good chance you have an alternator issue. Your engine sucks up and enormous amount of power, and without the alternator charging your battery is can quickly suck the life out of it.

5: Dead Battery

Sorry, I know this is chicken or the egg situation here, but one of the most common symptoms of a dead alternator? A dead battery!

As previously mentioned, your engine sucks power out of your battery faster than I suck down a Chick-Fil-A Cookies & Cream milkshake. Without a working alternator, this can tank your battery really quick, as your alternator is responsible for charging that bad boy.

If you’re seeing any of these symptoms or a combination of these, take your car to a mechanic as soon as possible. Don’t ignore an alternator repair – because if you do, it’s only a matter of time until your car strands you because of it.

Bonus: How To 95% Confirm Which One Has Gone Bad

I’ve been a big fan of GardenFork for quite a while, so it’s great to finally be able to shout him out here. This simple 10-minute video will help you test whether it’s the battery or the alternator.

If you have a “Check Engine” light, connect a code reader to the diagnostic port. If you find code P0562, you very likely have a failing alternator (note that codes may vary by vehicle make/model/year). Get it checked out, before it fails entirely.

Alright, So Your Alternator Is Busted. What Now?

Until your alternator is fixed, your car is essentially undrivable. You’ll need to arrange a tow into the mechanic in order to get your car fixed.

If you notice symptoms of a failing alternator, it’s incredibly important to get your car to the mechanic as quickly as possible. Once the alternator fails, your car won’t be drivable anymore, which means a potentially hefty towing bill unless you have AAA, or a vehicle service contract that provides free towing.

Can You Jumpstart A Car With A Bad Alternator?

A lot of times I get asked this when a client wants to bring in his or her vehicle after the alternator has blown. So, let’s clear this up.

Yes, you can definitely jumpstart a car with a bad alternator. But just because you can do something doesn’t mean you should. Let me explain.

Think about the last time you left the house when your phone’s battery was on 5%. Now, I don’t know about you, but leaving with 5% is a big no-no for me.

When you’re out and about if you know your battery is that low you’re probably not going to use your phone that much. To save the battery for when you really need it, you’d probably keep it in your pocket with the screen off. That’s all well and good, as keeping it on standby with the screen off doesn’t use that much power.

But, god forbid you get a phone call. What then? Your battery will be drained, and fast. Now it’s not a big deal if your phone goes dead, but the same can’t be said about the 2,000-pound murder weapon that is your car.

When you jumpstart your car, what you’re really doing is charging the battery. But you’re not charging it fully, not quite. When you charge the battery for a few minutes, you’re only going to have a few minutes to drive.

See where I’m going with this? If your battery decides to die while you’re on the road?

Yeah. Not good.

So How Far Will A Car Go Without A Working Alternator?

Your car’s battery should have a sticker somewhere on it that tells you the important specifications. The one we’re most interested in is the RC, which stands for reserve capacity.

The reserve capacity is a measure of time (in minutes) for how long your car’s battery will keep your headlights on and the engine running if it’s fully charged.

Using the example above, with an RC of 160 that means that the battery should be able to keep the engine running and the headlights on for 160minutes. Using things like the rear window defroster, the radio and the power windows (if you’ve got power windows) will shorten that amount of time.

I would also warn that running an engine on the battery alone, until the battery is dead, will drastically shorten the life of the battery, and using a new alternator to attempt and resurrect a dead battery will kill the alternator in short order.

But just because you can drive for whatever your battery’s reserve capacity is, doesn’t mean you should. Remember, this is with a fully charged battery. If your alternator has been going bad, your battery is not going to be fully charged.

What Causes Alternators To Fail?

Generally speaking, the alternator is a hardy part. The number one cause of alternator failure is perhaps unsurprisingly…

1: Your Alternator Is Old (Most Common)

I’m trying not to sound like a broken record here, but the most common reason your alternator just decided to up and quit?

It’s old. It happens.

The average alternator in good conditions can last for up to 10 years, assuming you’re driving your car lightly. With normal use, this can be as low as 5 years in more challenging climates (looking at you, New England and you Pacific Northwest).

2: Blown Fuse

Occam’s razor baby – start with the simplest explanations first and work backwards from there.

Vehicles use fuses to keep the alternator functional. These fuses blow out after a while or when there is a power surge. In these cases, your alternator would fail and your battery would not charge.

If you have a bad alternator, look in the owner’s manual to see where the alternator fuse is in your car and check to see if it is blown.

3: Broken Pully (Or Broken Pully Belt)

Alternators use the mechanical power of a belt and pulley to generate the electrical energy for the vehicle. This pully and belt system is the weak link in your alternator. The pully can stop working, while the alternator belt can wear out and break. The problem is that the alternator belt and pulleys are not too durable, which means they can easily break.

Pulleys will typically last for a long time before they eventually get damaged from old age. The pully only really gets damaged if you have an accident of some kind. Much more common is the belt itself wearing out.

Belts are flimsier and will eventually start to crack and even break after enough time. If either one of these things were to happen, there would be no mechanical energy being generated for the alternator to convert.

How Much Does It Cost To Fix An Alternator?

It’s typical for a typical alternator repair to run you between $300-$500 dollars, depending on your vehicle. This is for a re-manufactured alternator with labor included.

A new alternator on the other hand, can run you anywhere between $600-$800. The problem isn’t the part itself, which shouldn’t set you back more than a few hundred. It’s the labor.

Mechanic Joseph Rakoswi, the owner of Savage Automotive in Philadephia said “For the alternator, It could go anywhere from $200 to $800, “We had a vehicle recently that was four hours to remove and replace the alternator.”

Your cost is going to depend on how difficult it is to get to. As a general rule, the more labor intensive makes (think BMW, Mercedes, and the oh so reliable Jaguar) will generally costs more than a Honda or a Toyota.

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