It all starts with a few telltale problems: a dashboard light that comes on for a brief moment, maybe dimmed headlights and a few flashing gauges. Maybe your car even has a strange smell or you hear a growl coming from under the hood.
Is this a case of possession of your car? No. This is probably one of many possible alternator problems, and without some attention, the alternator can cause car problems ranging from slow starts to a dead car.
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| Top 10 Signs of Alternator Problems |
The alternator is a relatively simple component with only a few parts, but it plays a vital role in the operation of any gasoline-powered vehicle. Essentially, the alternator converts the mechanical energy of the engine's rotating crankshaft into electricity through induction. The wires inside the alternator cut a magnetic field; this in turn induces an electric current. This current is used to power your car's accessories, which can range from headlights to the electro-hydraulic elevators of a snowplow. (Electric vehicles do not need alternators because they are driven by a combination electric motor and battery that provides plenty of power for normal vehicle operations. Electric and hybrid vehicles, which do have alternators, often use regenerative braking systems to give the battery a boost).
Because the alternator is connected to (and critical to) other vehicle systems, any automatic mechanical problem can affect its operation and have an effect on the diagnosis of car problems. Paying attention to the 10 warning signs on this list can make diagnosing car problems caused by the alternator a little easier.
10: Warning Light
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| Warning Light |
In the dashboard of most cars built in the last decade is a warning light dedicated to signaling an alternator problem. In most cases, the light is shaped like a battery, although some 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 consult the owner's manual or a shop manual). Many people see this light and instinctively think they have a battery problem, which is a symptom that will be covered later, but that's not really why the light comes on.
That light is related to computer systems in the car monitoring the alternator output voltage. If the alternator output goes below or above a preset limit, the light on the dashboard comes on. Once the output is within the range, the light remains off. In the early stages of alternator problems, the light may appear to flicker - coming on for a second, then going off again. Or perhaps it only comes on when the accessories are activated.
For example, let's say it's nighttime, your headlights are on and everything is working perfectly. Then it starts to rain. When you turn on the wipers, the light comes on. You turn off the wipers and the light goes out. While this may initially seem like an aggravating problem, the warning light does its job exactly as intended.
Most alternators have an output between 13 and 14.5 volts that they try to keep at a constant level. As your car's headlights, windshield wipers, radio, heated seats, rear window defroster, etc., require more power, the alternator must work harder to maintain the necessary voltage. If your car's alternator is not working at its full potential, or if demands are placed on it that it can no longer meet, the voltage will go above or below the set level and turn on the warning light.
9: Dimmed Lights
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| Flickering Lights |
Since the alternator supplies your vehicle's electrical needs, when it begins to lose its potential, so do the car's accessories that use that electricity. Your car may begin to exhibit erratic symptoms ranging from dimming or extremely bright headlights and dash lights, to speedometers and tachometers that simply stop working for no apparent reason.
Your exact experience usually depends on a number of factors. The first is how much power the alternator is still producing and where it is in its death cycle. So how your car is programmed. In most new vehicles, automakers have some sort of pre-programmed priority list for where electricity will be sent in case an alternator problem occurs. This is usually based on safety considerations. For example, your car's heated seat will turn off or the radio will turn off before the headlights go out and disappear. This is because you need to be able to see in order to stop safely if your car suddenly dies - your radio and heated seats simply become secondary at that point.
8: Flickering Lights
On the previous page, you learned that dim exterior and interior lights are common symptoms of alternator problems. If your lights aren't really dim, they may be flickering instead. These two symptoms often go together, but not always. If your lights are bright, then dim, then bright again (either on a regular schedule or seemingly at random), then you definitely have a problem with your electrical system, and the alternator is the most likely culprit. The reasoning is the same as if the lights were simply dimmed - the alternator simply isn't generating enough juice to keep the lights on at full power, and instead of dimming all the lights in response, your car tries and fails, to maintain the proper light output.
If you want to be sure that the problem is the alternator, rather than something else in the electrical system, just look for a pattern. Can you identify that the lights are flickering when you do something else that uses electricity, such as turning on the radio, adjusting the air conditioning or using your power windows? This will be the key to helping you narrow down the possibilities, as it shows that your lights are flashing in response to the extra load on the system. As you continue to read this article, you will see that a failing alternator simply cannot keep up with all the things you are asking your car to do during a typical drive.
7: A dead battery
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| A dead battery |
While not technically an alternator problem, a car that won't start is a definite sign that there's a problem in the starting system. When the key is turned, you'll hear a telltale relay click, but nothing else happens. After a while, even this noise stops. The immediate problem is usually a dead battery, but you have to ask yourself, "Why is it dead?"
When an alternator starts to fail - or fails outright - the car battery starts to take over rather than act as a capacitor for the system by receiving a constant infusion of electrical energy from the alternator. However, even the best car battery will eventually discharge, leaving you stuck in the driveway or worse, on the side of the road. Car batteries are not designed for long-term use. They are designed to provide your vehicle with enough electrical power to start by feeding the starter with a burst of power and spinning the assembly. In other words, a bad alternator can get your attention by killing your car battery, even if the battery wasn't the problem in the first place.
Diagnosing a dead battery versus a dead alternator is relatively easy. Simply start your car, then remove the jumper cables as quickly as possible. Then wait. If the alternator fails to charge the system, the car will soon die again and you have identified the problem. However, if the car runs and continues to run, the problem is probably with the battery.
Be careful, though, because a dying battery can only receive a charge for so long and can become completely dead later despite the best efforts of the alternator. You can test the battery with a voltmeter, and most auto stores have the ability to check a suspect battery, usually for free.
6: Broken or Loose Connections
In this case, everything with your car's alternator seems to be working properly - no belt problems or other visible signs of trouble - but the car's battery is dead, as is most of the car's electrical equipment. This could mean that the alternator is producing electricity, but it's not going anywhere or it's the wrong kind.
The electricity from the alternator is carried by large cables and smaller wires. Any problem in the wires, cables or connections at either end can reduce or prevent electricity from flowing. Sometimes a symptom of this problem can be brighter lights as the alternator produces more power to overcome the resistance of a bad wire or broken or loose connection. This symptom is usually accompanied by a hot wire smell. Higher resistance in a wire creates heat, the same way an electric burner on a stove heats up by resisting the flow of electricity.
Another problem could be the alternator's diode rectifier. Alternators produce alternating current (AC) electricity in three phases, but car accessories require direct current (DC) to operate. The rectifier changes the current from AC to DC. Without this critical component working properly, the electricity produced by the alternator cannot be used.
5: Bad Belts
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| Bad Belts |
The following three symptoms are less obvious than a signal from a warning light; however, these signs of alternator trouble can tell the driver that something out of the ordinary is happening.
Mechanics are accustomed to customers complaining about typical alternator problems, then opening the hood to find the belt missing, hanging from the engine block or so loose that it's rattling around the engine compartment. Since a broken or loose belt is pretty obvious, take a look under the hood to see if your car has any of these problems, even if you're not skilled enough to fix them yourself.
If you're comfortable with basic maintenance and know your car's components, you're in good shape to catch a problem before it leaves you stranded. A quick visual check of the belt for cracks, excessive wear and other age-related issues can give an indication of a future problem. Keep in mind that the belt must have the proper tension to operate the alternator properly; too much tension is just as bad as not enough. A quick check of the belt tension is usually enough to determine if a problem exists. Be sure to let your car cool down before you start touching anything under the hood.
If the sight of a failing alternator isn't obvious enough to you (and it's perfectly understandable if it isn't), the sound can give you an idea. Drivers sometimes complain that they hear a "growling" or "whining" sound before an alternator gives out. The alternator is driven either by an accessory belt or by a serpentine belt in conjunction with the crankshaft pulley. The alternator pulley typically spins about two or three times faster than the crankshaft pulley to produce the power needed at lower engine speeds, such as at idle. The alternator pulley turns on a shaft, which in turn is supported by bearings or bushings. If the pulley is not properly aligned with the belt, if it is tilted on the shaft, or if the bearings and bushing are worn, the grunting or whining sound will tell you there is a problem.
Since many car problems cause strange noises, this symptom is most useful if it is associated with other symptoms, especially since it can be difficult to identify the source of a sound while driving.
If the alternator is so far gone that it has damaged your engine, you may hear rattles inside the engine caused by faulty engine bearings. Engine damage is one of the worst-case scenarios for alternator problems, and it's certainly a possibility, but it's so difficult and inconvenient to run a car with a bad alternator that you'll probably have it fixed long before it causes damage to your engine.
3: Strange Smells
Smell is the third sensory sign of an alternator problem, and it comes from your alternator working too hard on the verge of overheating.
Have you ever been near an electrical fire? An overworked alternator might smell a little like this. The hot wire smell can be caused by an overheated alternator pushing too much power through the rotor and stator.
Or hot rubber? Yes, that's another possibility, thanks to the rubber belt that keeps the alternator running, as well as the rubber sleeves on the wires that connect everything in your electrical system. A pulley that isn't aligned or spinning freely will cause more friction on the belt, which will create heat and then a burnt rubber smell. If these get too hot, your nose will probably know.
Not all bad smells indicate a potential alternator problem. The aroma is distinct from other car smells worthy of attention, such as the pungent smoke of burning oil, the sweet stench of overflowing coolant, or the burn of overheated brakes. Of course, none of these things are good, so if you smell one, get it checked out. And keep in mind that the absence of a bad smell doesn't mean everything is fine. In other words, an electrical bad smell will help narrow down the source of your problem, but it's possible for the alternator to fail without any of those accompanying smells.
2: Slow accessories
Do your power windows whine at your command to open or close? Does the stereo swallow CDs or the power sunroof lock in the open position? The features of modern cars are great until they're not, and the complex computers and wiring systems that run our electrical accessories offer more opportunities for something to go wrong.
Of course, it's possible for any of these features to go down at any time. Motors go bad, wires get crossed, and all sorts of problems can occur. If you notice an electrical quirk, you'll want to check that specific feature. If you're experiencing multiple problems at once, it's probably not a coincidence. Your alternator is one of the most likely sources of electrical problems, and you may not even notice that your car is running on reduced electricity until you make additional demands on the system, like turning on an interior light or trying to adjust your windows. Avoid using these features as much as possible until you can get your car checked out, to reduce the chance of an actual alternator failure.
1: Regular stalling or hard starting
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| Regular stalling or hard starting |
Because every car is different, difficulty starting your car or getting it to run is likely to be one of the first symptoms of an alternator problem. However, there are many other mechanical problems that can cause stalling or hard starting. It is important to look at everything that is going on with your car to identify the problem.
If your hard starts are, in fact, caused by an alternator problem, the reason is that the car is starting from the juice stored in the battery. As we've discussed before, if the alternator isn't charging the battery properly, the battery won't have enough power to start the car confidently and smoothly. If you stall even after the car has been running, the spark plugs may not be getting enough power from the alternator to keep the engine running. In other words, your battery isn't dead yet, but it's on its way out.
Careful readers may recall that a dead battery was mentioned much earlier in this list as a separate symptom, even though the mechanical factors are similar. Is it really worth addressing this separately, you might ask? The answer is yes - because it's much easier to ignore or dismiss a dying battery than a dead one, and if you know what this symptom means, then you have a chance to get your alternator checked out before you get stuck. .