How to Test an Alternator Without a Multimeter? Top 6 Easy Ways

Are you searching for an answer to the question: How to test an alternator without a multimeter? Automobile alternators are known for being one of the most crucial parts of a car. Their job is to create electricity for the car’s electrical system, which plugs in other moving parts like the starter, speaker system, and lights.

How to test an alternator without a multimeter

Without an alternator, you won’t have power to the car’s electrical system and will find it hard to start the car. Knowing how to test an alternator without a multimeter is a helpful skill. Especially, for anyone who likes to work on cars. It’s also a good trick to know if you have ever been stranded somewhere and your car battery has died.

There are some things you can try to test an alternator without a multimeter.

How do I test to see if my alternator is bad?

If there is a problem with your car’s charging system, it is usually indicated through an illuminated dashboard light. If this is not the case, there are still very simple ways how to test alternator regulator without a multimeter or a voltmeter.

We highly recommend ANCEL PB100 Automotive Power Circuit Probe Tester, 12V 24V Car Electrical Test Tool Kit AC DC Current Resistance Short Finder, Multimeter, Digital Voltage Meter, Test Light Diagnostic which you can buy on Amazon.

Method 1

The alternator is a crucial part of a vehicle’s operation. It helps keep the battery running by charging it with energy when the engine is running. And if there’s something wrong with the alternator, then you’ll see your lights dim as time goes by. So if you notice bright lights at first, but they start to dim, your alternator might be faulty.

Method 2

Run the car and disconnect the positive terminal of the battery. If the vehicle stops running, then you probably have a faulty alternator.

Caution: Do not test an alternator by disconnecting the negative battery cable, don’t do it. Although a good alternator should keep the engine running without the negative cable, this was never a reliable test with modern cars.

Method 3

Start your engine and rev your engine to 2000 RPM. The ampere or voltage gauge (if your car has one) on the instrument panel should be fluctuating slightly. If it isn’t or is reading low, the alternator isn’t charging the battery as it should.

Method 4

Open your hood and listen closely to the alternator while the engine is on idle. A squealing or screeching sound might indicate a problem with the alternator belt, and it becomes more apparent when you turn on all of the car’s electrical accessories.

Method 5

If you’re not sure about what’s happening, listen to a local radio station on the AM frequency. Tune the radio to its lowest volume setting. Switch off all of the car’s electrical systems and listen for an increase in noise from the alternator. If there is an increase in noise, this indicates problems with either the charging system or battery charge capacity.

How to test alternator with screwdriver?

Here’s another method how to test an alternator without a multimeter. If you have a screwdriver, and your car is off, you can check your alternator’s function using a screwdriver.

How to test alternator with a screwdriver

Ready to see if your alternator is working?

As mentioned above, alternator tests can be conducted in a variety of ways, but we prefer the alternator magnetic test.

Step 1

To do this test, you’ll need some items that contain metal, like a wrench or screwdriver. If you don’t have any on hand, you can find a spare one in most cars’ glove boxes.

Step 2

With your tool in hand, run it under the alternator while it’s running. A properly functioning alternator will produce an electromagnet that causes the tool to stick to it.

The magnetic strength will give you a good idea of how powerful your alternator’s electrical field is. If your tool doesn’t stick to the alternator, your alternator may not be producing electricity at all. Or it may be producing too little current for anything nearby to stick to it.

Can you test an alternator without a battery?

Can an alternator function without a battery? Yes, an alternator can produce electricity without a battery. An alternator will work even when the car is jump-started from another vehicle.

The alternator will also continue to produce power if the battery fails. However, the voltage regulator—in charge of regulating the flow of electricity—will not work.

How to test an alternator with a multimeter?

To test an alternator with a multimeter, check for a charge at around +14.2-14.7v while the car is running and under an electrical load, it shouldn’t drop below +13v from a full charge.

An alternator will supply a current of between 1 amp and 1.5 amps to each electrical device on the circuit. Devices like your radio can demand up to 10 amps of current from the alternator at higher RPMs and speeds. Here’s a step by step video guide on how to test an alternator with a multimeter from Junky DIY guy:

Why the alternator is important for your vehicle

It’s important to learn how to test an alternator without a multimeter. Your car uses electricity to run its lights, radio, and lots of other things. Your alternator generates this electricity by getting power from the engine and converting it into Alternating Current (AC). The alternator also regulates the flow of power.

When your alternator fails you will have a hard time starting your car because there won’t be enough power generated to turn over the engine. Your battery will also no longer charge because the alternator isn’t regulating the flow of electricity. And if you have a low voltage battery, won’t be able to use any of your car’s accessories—like air conditioning or heated seats.

Related Content: Timing Belt vs Drive Belt – What’s the Difference?


Whenever the lights start flickering, and you find that the battery is low on power, it is highly recommended to get it checked out immediately. If not done in time, there are chances for your car engine to fail to turn over and start, which can cost you a lot of trouble!

Alternators can also be tested using simple methods. This guide provides the basics on how to test an alternator without a multimeter. It will serve as a useful reference tool to help you troubleshoot any problems you may encounter.


The methods on how to test an alternator without a multimeter are just for emergency tests. Please do not do it repeatedly. Always refer to your car owner’s manual for disconnecting the battery as it may differ for each car model.

Still, the most reliable and safe way to test your alternator is using a voltmeter or multimeter. There are tons of cheap options you can buy online. Always have these simple tools as they may help in other car problems that you may encounter.

Be careful when disconnecting battery cables as it may cause short circuits if not done properly.

Leave a Comment