Home » Engine » 8 Signs Of A Bad Alternator: 2022 Guide | Symptoms + Solutions Inside

8 Signs Of A Bad Alternator: 2022 Guide | Symptoms + Solutions Inside

Car repairs are never fun, especially ones that are expensive. If you find yourself needing an alternator repair, you might be unable to drive your car until the repair is completed. That can lead to even more worry and stress. Alternators are critical pieces of your car’s charging system, so you will quickly know when you have a problem. So, just what is an alternator, and how much will the repair cost you? We will give you all the details you need to know about alternator repairs, including how to test your alternator and how much a repair should cost you.


What Is An Alternator & How Does It Work?

Your car alternator (alt) is like a small generator for your car. It creates electrical current by converting the mechanical energy from the running engine into electricity. As your serpentine belt spins the alternator, the rotor inside the alternator spins around magnetic poles. This process, known as magnetic induction, creates electricity. Since the magnetic poles alternate between North and South, the current created is alternating current. This means that the current changes directions frequently.

The alternating current is converted to direct current or DC power. This type of power can be used by your vehicle. So, what does an alternator do with this power? It is used to keep your battery charged as your vehicle is running, and it provides power to the many different electrical systems in your vehicle like the lights, radio, fuel injectors, and anything else that requires power to operate. Without a properly working alternator, your vehicle would not run very long. Your battery would drain quickly, and then you would be unable to restart the car.

8 Signs Of A Bad Alternator

So, how do you know when your alternator is going bad? The signs of a bad alternator are usually hard to ignore. If your vehicle is not getting enough power in the electrical system, then those symptoms generally show up quickly and obviously. Here is what to watch for.

— Voltage Warning Light

Most modern cars have computers and sensors that know exactly how much voltage your alternator should produce. This voltage output is constantly being monitored. If the volts drop below a certain threshold, then a warning light will illuminate on your dash. Most of the time, this light looks like a small battery. In some cases, your vehicle might illuminate the check engine light if it does not have a separate voltage light. If you see this battery light pop up, then make sure you get your car to a mechanic right away. If you don’t, you might find yourself stranded on the roadside waiting on a tow truck.

— Repeated Dead Battery

If you have a dead battery once, perhaps it was just an accident. Maybe you forgot and left your lights on. Perhaps you left your phone charger plugged in with your phone charging overnight. However, once you get a jump start and recharge your battery, that should not happen again. If you constantly have a dead car battery with no good explanation or reason, then your alternator could be the culprit. If your alternator is not recharging your battery as you drive, then it likely will not have enough power to crank the car again after you shut it off. A repeated dead battery might signal the need for an alternator replacement.

— Dim Lights

Your car’s headlights and interior lights require quite a bit of power to run them at full strength. With a properly functioning alternator, your lights should be constantly bright because they are running at full power. However, low alternator output can cause your lights to appear dim. Another telltale sign of an alternator problem is if your lights get brighter as your engine RPMs increase. If you step on the accelerator pedal and the lights get brighter, then your alternator is likely not putting out the correct amount of voltage. You should have it tested right away to see if it needs replacement.

— Erratic Electronics Behavior

Electronics can be finicky, especially if they are receiving an erratic amount of power. Most electronics today require extremely clean power — meaning that the voltage they receive needs to be very precise and constant. If your alternator is malfunctioning, it can have unintended consequences on your car’s electrical components. You might notice that your radio gets louder or quieter as you drive, a weird humming sound coming through your car speakers, or your power windows operating very slowly. If you notice any odd symptoms with your car’s electronics, then you might have an alternator problem.

— Car Stalls Frequently

Does your car stall frequently while driving? This could be due to many reasons, like a failing fuel pump, bad spark plugs, or clogged injectors, but it might also be due to a bad alternator. Nearly everything on your vehicle requires electrical power from the alternator. Without this electrical energy, key pieces of your engine may stop functioning, and when they do, the engine will shut off. If your car frequently stalls while driving, then you might have a faulty alternator causing the problem.

— Car Has Difficulty Starting

If the alternator is not properly recharging your vehicle’s battery, you will be able to quickly tell as soon as you attempt to start the car. In some cases, the car might not start at all. At other times, your car might only have difficulty starting. If you turn the key and notice that the engine cranks slowly when you start the car, it could be a bad alternator. Your local auto repair shop can determine whether you have a bad battery or alternator.

— Whining Noises

If you notice that your alternator is making a squealing or whining noise as the drive belt spins it, then you have a problem. It is likely on its way out, so make sure that you get it to a mechanic right away. Do not ignore this sound, as it could certainly leave you stranded.

— Weird Smells

In some cases, your alternator might actually output too much power. This can be especially true when the voltage regulator goes bad. In that case, you might start to notice a burning smell or the smell of sulfur. When your battery overcharges or too much power is sent to other electrical components, then you can smell the effects. If you notice strange smells from under your hood, then have a mechanic take a look.

How To Test Your Alternator

Testing your alternator is not that difficult. You will simply need a multimeter or voltmeter and know how to use it. With your vehicle running, the output of the alternator should be somewhere between 12 and 14 volts. You should also turn on some accessories like the radio and lights and make sure that the voltage stays constant once the accessories are drawing power. If the voltage falls below 12 volts or goes above 14 volts, then you have an issue that needs to be addressed.

Cost Of Alternator Replacement

So, how much does it cost to replace an alternator? Alternator repair cost varies based on the make and model of your vehicle. Some vehicles have alternators that are much easier to remove and replace than others. For example, the alternator on an old Chevrolet truck can be replaced by a mechanic in less than an hour. However, a new Honda Accord or Mercedes might require several hours of work to access the alternator.

On average, you can expect a bill of about $500 to replace an alternator. So, how much is an alternator? The new alternator cost itself will usually be around $150 to $200, plus another couple hundred in labor. You might find that some vehicles only incur a cost of $350 while it might cost you $1,000 to replace the alternator in your BMW. Independent automotive repair shops are generally less than the dealership, and you can find independent shops that perform great quality work.

In some cases, you might not need a brand new alternator. If only your voltage regulator has gone bad, then you might be able to have a mechanic replace only that part for a much lower price. If you are lucky and don’t need an entire replacement, then you might have a bill of under $200.

How To Perform An Alternator Repair Yourself

Some people choose to avoid the repair shop altogether and save some money in the process by performing this repair service themselves. These people will only incur the alternator price alone. So, can you replace an alternator yourself? The answer is yes, although it is much more difficult on some cars than others. First, make sure that you have tested your alternator and confirmed that it is bad before replacing it. If your vehicle is still under warranty, just let the dealer do the work for you since it won’t cost you anything.

If you decide to replace the alternator yourself, you are probably wondering how to replace an alternator. The job is not difficult as long as you can easily access the alternator. You will first need to remove the serpentine belt. Make sure that you make a note of the proper routing before removing the belt. Next, unbolt the alternator and remove the electrical connection. You will then reattach the new alternator and reconnect the electrical cables. Replace the serpentine belt and start your engine. Congratulations, you just swapped your alternator!

The Bottom Line

A bad alternator can force you to quickly find a ride because your vehicle will not run very long once the alternator goes out. Thankfully, diagnosing a malfunctioning alternator is fairly simple, and you can even do it yourself with a multimeter or voltmeter. If you determine that it needs replacing, then you will probably wonder, “How much is a new alternator?” You can expect to pay around $500 for a replacement in most cases. If you have an alternator that is easily accessible, you might even decide to do the job yourself and save some money.

Frequently Asked Questions

Is it worth it to replace an alternator?

In most cases, yes, it is worth replacing an alternator. Alternators will all eventually fail, and the cost to replace them is not extremely expensive. Thankfully, a failed alternator does not generally do any additional damage to your vehicle. You can replace the alternator and continue driving your car for many miles to come.

What can I do to prevent an alternator from failing?

An alternator does not really require any maintenance, so there is not much that you can do to prevent failure. However, the biggest thing that you can do is not to overload it. You should not run additional accessories on your vehicle like extra lights, sound equipment, or anything that would require too much voltage from your alternator. This can overwork the alternator and cause it to fail more quickly. Many people wonder, “How long do alternators last?” On average, an alternator should last for about 100,000 miles.

What are the benefits of having an alternator repaired?

The main benefit is the fact that you could continue to drive your car. You cannot drive with a bad alternator as your car will only run for 10 to 15 minutes before dying. Once the alternator is repaired, then your battery will charge like normal. This means that you can crank your car again after you shut it off, and all the electronic components will operate like normal.

Leave a Comment