How to Test Alternator by Disconnecting Battery?

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An alternator is a crucial part of the vehicle. It’s like the brain of the car. It utilizes the power created by the engine. However, it’s possible to have a damaged alternator at some point in life. And having a damaged alternator means having a hassle like never before. Moreover, if the alternator breaks down in the middle of the road it becomes extremely dangerous.

Here’s the thing- There are many ways of testing an alternator. And a popular way is by disconnecting the battery. So, how to test an alternator by disconnecting the battery?

Well, the answer lies in the question actually. However, we will discuss the process in brief here. Now, let’s charge right into the details-

Symptoms of a Failing Alternator

how to check for bad alternator by disconnecting battery

Before going directly to the test, it’s better to understand whether it is the fault of the alternator or not. However, just like any other parts, the alternator gives out some clear signals while going out.

So, here we are with 5 symptoms of faulty alternator-

  1. Your warning indicator light will start going. This is the first and foremost symptom of a failing alternator. It’s okay to be confused about what light it is and everything. You’ll find a light labeled as ‘GEN’ or ‘ALT’.
  2. Headlights will start flickering. This happens because alternators supply power to the headlights. As a result, this is quite a strong indicator that your alternator is struggling. Sometimes the headlight gets dim instead of flickering.
  3. All electrical components will start misbehaving. But some components are directly linked with the alternator. If those start misbehaving, then further inspection is a must. Those parts are- the dashboard lights, power windows and locks, air conditioning, and radio.
  4. Your car will stall if the alternator goes bad.  The alternator supplies electricity to your spark plugs. So, if there’s a problem with the alternator, your vehicle will stall. And from time to time, it’ll be difficult to start the car.
  5. Your battery will die. If the alternator goes bad, your battery will get drained pretty fast. As a result, you’ll stumble upon a dead battery every week or so. The battery might get dead even overnight.

If your condition matches with 2 or 3 symptoms from here, you should take a quick test for confirmation.

Testing Alternator by Disconnecting Battery

So, how do you check an alternator by disconnecting the battery? Well, this is a quick and simple process. Here we have dissected the whole process into several steps.

Now, let’s look at the steps-

  • Park your car in an open but safe place. For this, you can use the driveway. If you have pets, then take those to a safe distance.
  • Open up your hood. Double-check if the car is in a stable position.
  • Go to your driver’s seat.
  • Start the engine. You probably will face some difficulties at this point if your alternator has problems.
  • Get out of that seat once the car goes running.
  • Go to your battery.
  • Disconnect battery while the car is running.
  • See if the car is running like before.

If your vehicle keeps on running like before, then congratulations your alternator is okay. It’s possible that some other part of your vehicle has problems.

However, if the vehicle stops, then your alternator has some problems for sure.

And that is how to check for the bad alternator by disconnecting the battery.

Criticisms of Battery Disconnecting Test

test alternator by removing battery cable

It’s super easy to test alternator by removing battery cable. But it’s super risky too. Moreover, experts have nowadays shown concerns about the effectiveness of this method.

So, where’s the problem?

This method was quite effective for generators. But the alternator isn’t a generator. An alternator is internally regulated. So, when you test alternator by pulling battery cable you increase the probability of killing that regulator.

That was the risk of it. Now about the ineffectiveness of it-

The vehicle will run if the alternator is producing enough juice. But it’s also possible that the alternator is actually in a bad shape but is producing enough to run the engine.

As a result, you’ll have a false indication that the alternator is good.

To be honest, many people have fried their vehicle internal components by using this method. Some guy reported that all his vehicle bulbs broke out after using this method.

So, it’s better to avoid this method.

Testing Alternator in the Right Way

How to Test Alternator by Disconnecting Battery

The battery pulling method is a bad choice. So, what’s the good one? Well, the answer is using a multimeter.

You can test your alternator in 3 easy steps by using a voltmeter-

  1. Get a multimeter (Our pick: AstroAI Digital Multimeter) and turn on the car while keeping all the accessories off.
  2. Get reading in between the battery terminals by using the voltmeter.
  3. Turn on all the vehicle accessories. Get another reading in the same way.

If the first reading shows 14V, then your alternator is good. If the second reading shows 13 volts, then your alternator is good too. Any reading other than these is clear signs of a bad alternator.

But while performing this test, make sure that your vehicle is in a safe position.

However, if you have time then try out the full field test. It’s a bit complex and time-consuming but it is the best test out there.

Final Thoughts

Now, you know how to test alternator by disconnecting the battery. To be more specific, you know about the alternator failing symptoms, the reason behind avoiding this test and an alternate test.

Our number one goal is to help you to keep your vehicle in its best condition. So, even though you’ve asked about that specific test, we’re telling you to avoid that.

No matter whatever test you follow, don’t forget to put on safety measures at first. And if there’s any problem with your alternator, don’t make delays in repairing it. To be more specific, take the vehicle to an expert. Change the alternator if it’s required.

Good luck. Happy driving.

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