Will a car shut off with a bad alternator?

4 Symptoms of a Faulty Alternator

Today’s automobiles make use of two different power sources: mechanical and electrical. Your engine generates mechanical force through combustion, thus providing the power needed to move your wheels. Meanwhile, an array of other systems from your headlights to your radio rely on electrical power provided by your battery.

These two systems interact by means of the alternator, which transforms mechanical energy into electrical energy, thus keeping the battery charged. When an alternator stop working correctly, a wide range of problems may ensue. This article takes a closer look at four commonly experienced symptoms of a failed alternator.

1. Car Won’t Start

A dead battery almost always lies behind a car that won’t start. If you jump-start the car and it runs correctly, the problem likely stems from the battery itself. In some cases, the battery may have just become drained — for instance, if you forgot to turn your lights off. In such cases, jumping the battery and allowing your car to run for a few minutes fixes the problem.

If your car remains running once jumped, yet won’t turn over the next time you try to start it up, you may need a new battery. Because the car continues to run once started, you know that the alternator remains capable of performing its function. Instead, the battery does not seem capable of holding a charge with the engine off.

If your engine dies again within seconds or minutes of jumping the battery, the fault probably lies with your alternator. In fact, your alternator may have died completely. Installing a new battery may relieve the problem for a short time. Yet, once the new battery has discharged its power you’ll be stuck with a car that won’t start again.

2. Engine Stalling

A dead alternator almost always leads to a car that won’t start. Yet, before things get to that point, you may experience a range of other problems. A faulty or dying alternator may only work in fits and starts. As a result, the alternator may not have what it takes to keep your battery fully charged — even with your engine running.

As a result, you may find your car stalling out at odd times. The immediate cause of such stalling often lies with the fuel injectors, which require electricity to do their job. If a faulty alternator fails to keep your battery consistently charged, the fuel injectors may not fire, causing your engine to stall.

3. Electrical Issues

A dying alternator can lead to a wide range of other electrical issues. Generally speaking, such issues manifest as an inability to perform at normal power. For instance, you may notice that your headlights seem dimmer than usual — or even that their brightness fluctuates inexplicably.

Other signs include dash and dome lights that 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 shut themselves down periodically.

4. Unusual Sounds

Bad alternators often produce loud or unusual sounds. An alternator receives its mechanical energy from the engine by means of a belt. If this belt has become misaligned or excessively worn, you may notice odd squeaking sounds coming from beneath your hood. A worn belt may fail to turn the alternator rapidly enough to generate adequate power.

The inside of the alternator contains bearings that allow the internal stator to spin in tandem with the belt. Over time, these bearings become pitted and worn, producing a humming sound. This sound intensifies as the bearings degrade further and further.

If you have noticed any of these symptoms, seek professional assistance as soon as possible. Even if your car continues to run, the alternator may soon fail completely, leaving you stranded. For more information on how to recognize a faulty alternator, please contact the automotive repair experts at Evans Tire & Service Centers for an appointment at any of our locations.

Can You Jump Start a Car With a Bad Alternator?

When the car starting battery is discharged, one can jump-start a car with another car’s battery using jump-start cables or using a car jump starter.

However, there are many reasons why the battery is dead in the first place, including parasite load over a longer period of time, a bad or simply old battery, or a bad or faulty alternator.

If the battery is almost new and there are no loads that would discharge the battery, and one nonetheless has to jump-start the car, there is a great probability that there is something wrong with the alternator or charge regulator, leading to the question if the car can be jump-started with a bad alternator.

Updated: January 25, 2023.

The answer is simple — Yes, You can jump-start a car with a bad alternator.

But, can You drive such a car, and for how long, that is another question.

Bad or Faulty Alternator or Charge Controller

When the car’s alternator or its charge controller goes bad, the car’s battery is not being charged, or it is being insufficiently charged.

Modern cars depend on electric power heavily, not just for powering alarms, GPS, maps, multimedia devices, etc., but also for powering the car’s central computer, fuel pump, and a few more critical components which doesn’t require much power, at least not as some multimedia devices, but nonetheless, they do require a reliable source of electric power.

What happens when the engine is running, and the car battery voltage starts to drop?

Signs of Alternator Problems

Well, first, the car will warn the user about a voltage drop, but the engine will continue to run — in most cases, this message will be in the form of a warning or stop message.

But, after some time, either the fuel pump will stop causing the engine to stop, or the central computer will stop causing the engine to stop too, or the computer will shut down the engine to prevent any damage and signal «General Electric/Electronic Failure» or will give some similar error message.

Of course, a large «Stop» on the dashboard will signal the user to stop the car before all of this happens, but if You wondered what would happen if You decide to ignore the dashboard’s «Stop» sign, now You know. 🙂

However, if the alternator is providing at least some power to the car, it is possible to jump-start a car and drive it directly to the car’s repair shop — just be sure to turn off everything that is not essentially needed.

Note: even before the onboard computer warns the user about upcoming problems, the user can spot typical signs of a bad alternator/discharged battery in the form of slow/lazy starts, dim lights, frequent engine stalling, the smell of burning wires or rubber, whining and other odd noises, malfunctioning electronics, etc. If You spot any of these signs, take your car to the mechanic to run some diagnostics. It can save You plenty of time in the near future.

How to Jump-Start a Car Using Jumper Cables?

To jump-start a car using jumper cables, one needs another car with a good battery and working alternator.

So, park the second car (one with a good battery) next to the first car (one with a discharged battery) and:

• connect a red clamp of the jumper cable to the positive (+) terminal (usually the red one) of the dead battery,
• connect the other red clamp of the jumper cable to the positive (+) terminal (the red one) of the good battery,
• connect a black clamp of the jumper cable to the negative (-) terminal (usually the black one) of the good battery,
• connect the other black clamp of the jumper cable to the negative (-) terminal (the black one) of the bad battery,
• let the second car run for a few minutes — this will provide some «surface charge» to the bad battery and help both batteries crank the engine.

Note: while being connected, the alternator of the second car is under a larger than-normal load, so don’t keep the cars connected for a very long time.

After the first car cranks its engine, disconnect the cables in reverse (start with the negative clamp from the bad battery).

If the first attempt was not successful (the electric system of the first car didn’t have enough charge/power for the car’s starter to kick in), let both cars stay connected for a few more minutes — just be sure to monitor the dashboard of the second car, just in case — and try again to crank the first car’s engine.

If it starts, good — disconnect the jumper cables, turn off everything non-essential and drive to the car repair shop.

If it doesn’t start — disconnect the jumper cables, and call the tow service.

Disconnect the cables in reverse, starting with the negative clamp from the dead/bad battery.

How to Jump-Start a Car Using Car Jump Starter?

Car jump starters are small and compact devices that feature lithium rechargeable batteries and control electronics that enable them to provide insanely strong currents, considering their weight and size — and they are relatively cheap as well.

A good car jump starter can fit most glove compartments and backpacks and can be carried around — just be sure not to leave them in the car during freezing cold days or hot summer days.

If the car’s engine doesn’t want to start, connect the jump starter to the battery (starting with the positive clamp!), turn ON the jump starter, let it analyze the battery, and when the jump starter signals, crank the engine — it is that simple.

Note: lithium jump starters are very easy to use, but their exact starting procedures may differ a little bit, so keep the Owner’s Guide with your car jump starter, just in case.

Disconnect the jump starter and if You suspect that the bad alternator and/or charge controller are the reason for heaving dead battery, drive directly to the car’s repair shop — just be sure to turn off every non-essential electric load.

Frequently Asked Questions (FAQ)

Here are some of the most common Frequently Asked Questions (FAQ) about cars, alternators, batteries, and similar.

Will a car start with a bad alternator?

If the engine’s starter is provided with enough energy, it will start the engine regardless of the alternator’s condition.

Now, does that energy come from the onboard battery, or is it provided by jumper cables or a portable car jump starter, that is another question.

Will a car run with a bad alternator?

Maybe, depending on the remaining battery charge — if the alternator is bad, the battery must supply power for various electric and electronic systems, which can drain the battery rather quickly, especially if the battery was already rather discharged.

How can I tell if my alternator is bad?

After starting the engine, the car’s voltage is still very low. Also, revving up the engine doesn’t increase the line voltage. Of course, You can also run diagnostics.

Would a bad alternator cause no start?

A bad alternator causes discharged battery, which is then unable to crank the engine properly, so yes, one can say that a bad alternator causes the engine not to start.

How do you tell if it’s your battery or your alternator?

Run diagnostics, for short.

However, if You manage to crank the engine using jumper cables or a car portable jump starter, and the car’s voltage increases, especially when the engine revs faster, then the alternator is (probably) good, and the battery is either discharged (let the engine run for at least 30 minutes, let it rest for 5 minutes and then check the voltage and try to crank the engine) or it simply can’t accept a charge — it is dead.

If You manage to crank the engine, and the car’s voltage doesn’t change, either the alternator or charge controller/regulator are bad and must be repaired/replaced. Also, since the battery is discharged, consider recharging it ASAP to prolong its operating lifetime.

Long Story Short: As one can see, there are several ways of cranking the car’s engine with a discharged/bad battery.

However, the question is if that car is safe for driving — after cranking the engine, check the dashboard and if there are no errors or warnings, drive to the repair shop.

Also, if You are using car jumper cables, having two cars connected for a longer period of time can overload the alternator and/or charge controller of the car with a good battery — again, keep your eyes on its dashboard.

Whatever You do in such a situation, stay safe — after all, it is your own responsibility.

Starting Problems? How to Tell If It’s the Battery or Alternator

If your vehicle won’t start, it’s usually caused by a dying or dead battery, loose or corroded connection cables, a bad alternator or an issue with the starter. It can be hard to determine if you’re dealing with a battery or an alternator problem. Here’s how to know which one is the culprit.

Bad Battery Symptoms

If the cranking of the engine is sluggish, like your vehicle is harder to start on cold mornings, it starts inconsistently, or there’s no sound and interior lights when you try to start, suspect a failing battery, a loose or corroded connection or electrical draw. A low battery that has visible corrosion on the terminals is probably damaged.

If jumpstarting works, then you know you’ve got a battery problem. But you also need to figure out whether it’s simply at the end of its life or there are underlying issues. A dead or low battery can be caused by a failing alternator. It can also result from additional draw from auxiliary lights, fuses, sound systems, alarms and such.

Signs of a Bad Alternator

Some of the things to look for are no-starting and trouble starting, dimming lights and problems with stereo system output. If your car starts but stalls when you’re underway, your battery is probably not being recharged due to a faulty alternator. A squealing sound coming from the engine that gets louder when drains like the heater or sound system are on may be your alternator bearings.

Another telltale is turning the AM radio to a low number on the dial without music, then revving the engine. If you hear a whine or the sound goes fuzzy when you hit the gas, your alternator is probably failing.

If the vehicle won’t crank or start but the headlights are still working, look to problems with the starter or other parts of the engine.

If you have a check-engine or battery indicator light illuminated on your vehicle, it could indicate a problem with an automobile charging system, or if your vehicle gets a jump-start and immediately stops running, it could be an indication that the alternator is malfunctioning. It’s important to bring this into a professional for a proper diagnosis.

What the Battery & Alternator Do

An auto battery supplies a big electric charge that travels through the starting system and turns some gears to start the car. Once the car is running, the alternator sends current back to recharge the battery as you drive. It supplies power for your car’s electronics when you’re underway and makes sure the right amount of charge goes back to the battery.

If Your Car Won’t Start

The common signs above should help pinpoint what exactly is going wrong.

If you’re not wanting to do your own diagnostics, get a jumpstart (and keep your vehicle running) and take it in for a technician to check your electrical system. Both the starting and charging systems should be inspected.

Battery checks on standard wet-cell batteries should include inspection of fluid level, the posts (the terminals marked + and -) for corrosion, and cables for snug connection and no corrosion.

An electronic battery test should be done, which gives more information than a standard load test. It measures the voltage and cold cranking amps (CCA). (Battery inspections and charges are free at Les Schwab Tires.)

The shop should also check the alternator’s voltage and current output and look for signs of bad diodes, the components that convert electrical current from AC (alternating current) to DC (direct current). If it’s time to replace it and your vehicle has been customized with power-hungry aftermarket accessories like a sound system, ask if you need a higher-capacity alternator.

If the alternator is working fine, the search for the problem will move to other parts of the starting and charging system.

Got a Bad Alternator?

It may have damaged your battery. Since the alternator regulates how much electric current gets fed back to the battery during recharging, the battery may have overheated due to overcharging. This shortens its expected life and can make it unreliable. Ask whether you need a replacement if you’re having alternator repairs done.

If it’s your battery that’s bad, it won’t damage the alternator.