How To Tell If Your Alternator Is Dead – An alternator is a relatively simple component consisting of just a few parts, yet it plays an important role in the operation of any gasoline-powered vehicle. Phuchit/ThinkStock
It all starts with a few telltale issues: the dashboard light comes on for a while, maybe the headlights are dim, and some gauges are flickering. Maybe your car gives off a strange smell or you hear a growl coming from under the hood.
How To Tell If Your Alternator Is Dead
Is this a case of your mischief? Not. This is likely one of many possible alternator problems, and if left unattended, the alternator can cause problems for your car, from slow starts to a dead car.
What Does An Alternator Do?
An alternator is a relatively simple component consisting of just a few parts, yet it plays an important role in the operation of any gasoline-powered vehicle. Basically, a generator converts the mechanical energy of the engine’s rotating crankshaft into electricity by induction. The generator wires cut the magnetic field; this, in turn, induces an electric current. That current is used to power your car’s accessories, which can be anything from headlights to electro-hydraulic snowplow lifts. The alternator also keeps the battery fully charged, providing the power needed to start the car. (Electric vehicles do not need generators because they are powered by a combination of electric motor and battery, which provides plenty of power for normal vehicle operation. EVs and hybrids that do have generators often use regenerative braking systems to give the battery an extra boost. .)
Since the alternator is connected to (and is important to) other vehicle systems, any mechanical issue can affect its operation and affect the car’s troubleshooting. Paying attention to the ten warning signs on this list can make diagnosing car problems caused by the alternator a little easier.
When generator power drops below or above a preset threshold, your car’s warning light will come on. In most vehicles it looks like a battery. Balloon111/ThinkStock
Most cars built in the last decade have a warning light on the instrument panel that indicates a problem with the alternator. In most cases, the light is shaped like a battery, although some will display “ALT” or “GEN” meaning generator or generator respectively. (On some older cars, the alternator is called the alternator, which might help you know if you’re looking at the owner’s manual or the shop manual.) Many people see this light and instinctively think they have a battery problem. which is a symptom that will be addressed later, but is not actually the cause of the light not coming on.
How To Test & When To Replace A Dead Car Battery
This light is connected to the car’s computer systems that monitor the output voltage of the alternator. If the generator power drops below or above a preset limit, the indicator light will come on. If the output is within range, the light will remain off. In the early stages of alternator problems, the light may appear to flicker – only on for a second and then off again. Or it will only light up when the accessories are activated.
For example, let’s say it’s night, your headlights are on and everything is working fine. Then it starts to rain. A warning light comes on when the windshield wipers are turned on. You turn off the windshield wipers and the warning light goes off. While this may seem like an aggravating issue at first, the warning light does its job exactly as it is intended.
Most generators have an output voltage between 13 and 14.5 volts, which they try to keep constant. Since your car’s headlights, wipers, radio, heated seats, heated rear window, and so on require more power, the alternator has to work harder to maintain the required voltage. If your car’s alternator is not running at full capacity, or if it is being placed under demands it can no longer meet, the voltage will rise above or below the set level and a warning light will come on.
A faulty alternator can cause electrical interference that can cause erratic headlight problems such as frequent dimming or extreme glare. Zunnie/ThinkStock
What Are The Symptoms Of A Bad Alternator?
Since the alternator covers your vehicle’s electrical needs, if it starts to lose its potential, so will the car accessories that use that electricity. Your car may have fluctuating symptoms ranging from dim or extremely bright headlights and dashboard lights to speedometers and tachometers that just stop working for no apparent reason.
Your exact experience will generally depend on several factors. The first is how well the generator is still producing power and also where it is in its death cycle. The second is how your car is programmed. For most new vehicles, manufacturers have some kind of pre-programmed priority list to which electricity is sent in case of alternator problems. This is usually based on security considerations. For example, your car’s heated seats turn off or the radio turns off before the headlights dim and go out. That’s because if your car suddenly stalls, you need to see it to pull over and stop safely – your radio and heated seats become secondary at that point.
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 could be flickering. These two symptoms often go hand in hand, but not always. If your lights are bright, then dim, then bright again (on a regular or seemingly random beat), then you definitely have a problem with your electrical system, and the most likely culprit is your alternator. The reasoning is the same as if the lights were dim – the alternator just isn’t producing enough juice to keep the lights on at full power, and instead of dimming all the lights in response, your car will try, but fail, to maintain the correct light output.
If you want to be sure the problem is with the alternator and not something else in the electrical system, look for a pattern. Can you spot the lights that flash when you’re doing something else that uses electricity, like turning on the radio, adjusting the air conditioning, or operating the power windows? This is key to helping you narrow down the possibilities as it shows that your lights are flickering in response to the extra load on the system. As you continue reading this article, you will see that a failing alternator simply cannot do all the things you ask your car to do during normal driving.
What Are The Signs Of A Bad Alternator?
A bad alternator can kill your car’s battery, even if the battery wasn’t the problem to begin with. Natnan Srisuwan/ThinkStock
While not technically an alternator problem, a car that won’t start is a clear sign that the problem is with the starting system. When the key is turned, you hear the relay ticking indicator light, but nothing else happens. After a while even this noise stops. The immediate problem is usually a dead battery, but you should ask “Why is it dead?”
When the alternator starts to fail or fails, the car battery starts to discharge, instead of acting as a capacitor for the system, getting a steady infusion of electricity from the alternator. But even the best car battery will eventually die, leaving you stranded in your driveway, or worse, on the side of the road. Car batteries are not designed for long-term energy use. They are designed to provide your vehicle with enough electrical power to start the engine by firing the starter motor at high power and getting everything revving. In other words, a bad alternator can get your attention by killing your car’s battery, even if the battery wasn’t the problem to begin with.
Diagnosing a dead battery and dead alternator is relatively easy. Just start the car and remove the jumper cables as quickly as possible. So 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.
What Does An Alternator Do?
Be careful, however, as a low battery can only hold a charge for so long and may run out of power later on despite the generator’s best efforts. You can test the battery with a voltmeter, and most stores offer options for checking a suspect battery, usually for free.
In this case, your car’s alternator appears to be fine — no belt issues or other visible signs of trouble — but your car’s battery is dead, as are most of your car’s electrical systems. This could mean that the generator is producing electricity but it’s not going anywhere or it’s not the right type.
Generator electricity is conducted through large cables and smaller wires.
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