If you’ve heard the term “alternator” before, you probably know that it’s an essential part of your vehicle. But what exactly does an alternator do? Simply put, your alternator keeps your car battery charged so you can turn on your car and use electronic accessories like your headlights and radio.
If you are having alternator problems, you may find that your car will not start or stay on for more than a few minutes. Before that happens, however, you’ll likely encounter one or more of these signs of a bad alternator.
7 Symptoms Of Bad Alternator
1. Dim Lights
The symptom of a bed alternator that most drivers recognize is dim or flickering lights. Headlight dimming is one of the first signs that your alternator is starting to fail. If you notice your headlights getting brighter and dimmer as you increase or decrease the speed of your engine, that is a warning sign. An alternator that is in good working condition will ensure bright headlights, no matter what speed you drive.
In addition to flickering, your headlights can also weaken or grow dim. Dim lights on the dashboard also indicate a problem. Both flickering and dimming are strong indicators that your alternator is no longer able to produce sufficient power.
2. Battery Light
There is a warning light in the instrument cluster of most cars built in the last decade to indicate a problem with the alternator. In most cases, the light takes the form of a battery, although some will display ‘ALT’ or ‘GEN’, meaning alternator or generator respectively.
In some older cars, the alternator is called a generator, which can be helpful if you’re looking through the owner’s manual or a workshop manual. A lot of people see this light and instinctively think they have a battery problem, which is a symptom that will be addressed later, but that’s not really why the light comes on.
This light is connected to computer systems in the vehicle that monitors the alternator output voltage. When the alternator output drops below or exceeds a preset limit, the dashboard lights up. Once the exit is within range, the light will remain off.
In the early stages of alternator problems, the light may appear to flicker – just on for a second and then off again. Or maybe it only lights up when accessories are activated.
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3. Bad Alternator Sound
A bad alternator will make a high-pitched whining noise. There may also be a grinding noise, and you may hear it knocking or squeaking. If you’re not sure if your alternator is bad, it’s best to have it checked out by a professional.
An alternator has many moving parts that rotate when working properly. If one of these parts begins to work ineffectively or breaks off, you may hear unusual noises. If you hear a grinding noise in your car, it could indicate that the alternator is going bad. The grinding noise can be caused by a worn bearing.
Your car can also make a howling noise when the voltage regulator is sending signals to the alternator to charge more than it needs to. If you hear any howling or grinding noise, that’s a good indication that your alternator needs to be checked.
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4. Electrical Issues
A dying alternator can lead to a variety of other electrical problems. In general, such problems manifest themselves as an inability to work with normal performance. For example, you may find that your headlights appear dimmer than usual – or even that their brightness varies inexplicably.
Other signs include dashboard and overhead lights, which may also flicker or appear dim. Automatic windows may open and close much more slowly than usual. Or your radio and/or entertainment centers may turn themselves off periodically.
5. Engine Stalling
A bad alternator almost always results in a car that won’t start. But before things get that far, you may encounter a number of other issues. A faulty or dying alternator may only work intermittently. As a result, the alternator may not have what it takes to keep your battery fully charged—even with the engine running.
As a result, your car may stall at unusual times. The immediate cause of such a stall is often the fuel injectors, which require power to do their job. If a faulty alternator isn’t keeping your battery constantly charged, the injectors may not fire and your engine will stall.
6. Dead Battery
Sometimes a dead battery is just a dead battery — it’s reached the end of its life after a few years of use — or maybe you accidentally left the headlights on all night. Other times, however, a dead battery could be a sign that your alternator is malfunctioning.
A bad alternator won’t sufficiently charge the battery while the engine is running, causing the charge to deplete faster than usual. One way to test whether the issue is battery- or alternator-related is to jumpstart the car.
If you jumpstart your car and it stays running, your battery may need replacing soon. However, if you jumpstart the car and it dies again shortly after, it might mean your alternator isn’t getting enough power to the battery.
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7. Smell Of Burning Rubber Or Wires
A foul smell from b burning rubber or wiring could indicate that parts of your alternator are starting to wear out. Because the alternator drive belt is under constant tension and friction—and because it’s close to the hot engine—it can wear out over time and give off an unpleasant burnt rubber smell.
Similarly, if your alternator is overloaded or has frayed or damaged wires, you may smell a burning odor that is comparable to an electrical fire. An overloaded alternator tries to force too much current through its wires, causing them to heat up unsafely. Damaged wires also create resistance to the flow of electricity, causing the wires to heat up and give off a foul odor.
When you start noticing certain issues, it’s time for an alternator replacement. You can go to your local auto shop to get this work done. But you should be prepared for a hefty bill. Find out more about How Much Does It Cost To Replace An Alternator?
How To Diagnose A Failing Alternator?
If you have a “Check Engine” light on, connect a code reader to the diagnostic port. If you find code P0562, you most likely have a faulty alternator (note that codes can vary by vehicle make/model/year). Get it checked out before it fails altogether.
If you suspect a bad alternator but don’t have a warning light, open the hood and check the condition of the belt. If it looks glassy and slightly burned, that’s an indication it’s slipping. The belt is too loose so it slips on the pulleys instead of riding along them.
The metal-to-rubber friction heats the belt and wears it out quickly. Adjust the tensioner so the belt is just right (too tight can also damage an alternator’s bearings) or replace the serpentine belt as it is one of the cheapest auto parts you can buy. It should be a quick and easy fix.
If everything looks good under the hood, grab your multimeter and test your alternator to the norm. If any of the voltages are below the recommendation, this is a strong case for a new alternator. Also, if you check all of your wiring for corrosion or a loose connection, you may find that you need new alternator connectors, rectifier sets, or brush sets.
