How to test alternator without voltmeter

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The most popular alternator test without a multimeter is when you start your engine and disconnect the negative terminal of the battery while it’s running, it will not have any effect on your engine if the alternator is in good working condition. On the other hand, if the engine will stop working while the terminal is disconnected, that means you have a problem with your alternator.

This guy shows how you can check if your alternator is in good working condition (and if it is, you should look for a problem elsewhere):

Here is another video on checking if the battery is a problem or the alternator:

Is this a good test? Well, let’s assume that you are in a situation without any electrical measurement devices available, and gotta do something…

On the other hand, this test is considered not to be safe for you (see below), your alternator, or your internal computer. This is due to high voltage spiking upon reconnecting. Professionals do NOT recommend doing this test.

Not to mention, this test is not fool-proof and to know for sure you will need some electronic measurement device like a multimeter or voltmeter.

** Warning! This is NOT a safe test and you are doing it at your own risk, this is especially true if you disconnect the positive terminal first.

More alternator tests and clues

Whenever you find your car battery out of steam, you think immediately about a bad alternator. Below are some alternator tests and clues to look for if you don’t have a multimeter handy:

#1. Good battery and no start

If you just got a brand new battery and your car is not starting, then you definitely have a faulty alternator on your hands.

#2. The car dies after a jump start

If your jump-started car dies right after disconnecting jumper cables, the alternator could be your problem.

#3. Running car dies after disconnecting the alternator from your battery

Do this test at your own risk and try not to touch anything that can ground you. Disconnecting the negative terminal first and then positive, is less risky.

#4. The car does not pass the accessory test

While your vehicle is running, turn on anything you can think of in your car (headlights, radio, interior lights, air conditioning) and if any of it will take the engine down, then something is wrong with your battery charging system.

#5. Bad battery light clue

If the battery light on your dashboard is always showing that there is a problem with your battery, that could mean that it is not being charged. This is especially true for newer batteries.

If your battery is older and “more than slightly” overused, you may actually want to get a multimeter to check it out.

#6. Dimming lights clue

You will need some kind of light source for this test. Once you have it and your car is running, turn on your headlamps and see what happens.

If your test light dims for a second and goes back to normal, then the alternator just kicked in and everything is fine. You can start up more accessories and see if any of them will take the test light down.

#7. Sound test clue

If your engine is running and there is a problem with your alternator, you may actually be able to hear a squealing sound. Try turning on some car accessories as well while listening to see if the sound gets louder.

There is also an old-fashioned trick where you can listen for alternator noise through the use of a long screwdriver.

#8. Magnetic test clue

The logic behind this test is that if the alternator is not generating any power, then the rotor and stator will NOT have any electromagnetic field.

• Test #1. Turn your ignition into ON position (do not start) and touch the alternator pulley with a metal object like a wrench or screwdriver. If it sticks, the alternator is doing its job, if not, you have a problem.
• Test #2. Start your engine and let it reach an idling RPM. Touch the body of the alternator with the metal object and if it sticks, then everything is fine with your stator coil.

If any of the mentioned parts are hard to reach DO NOT do this test.

#9. Driving clues

If your lights are dimming while driving, and your radio and heater stop working, you might have a problem with the alternator.

#10. Doom test

If your car gauges start acting weird or stop working at all and your battery keeps on dying, these are good clues to alternator problems. If your car is not cranking or starting, check if your battery is in good shape, and if it is, you probably have a problem with the alternator.

Feel free to save the infoPin below for your future Reference :

So, is it an alternator or a battery?

Older batteries could actually be at the end of their life cycle and that needs to be checked for before blaming it on the alternator. If your car is not even starting in order to test it as mentioned above, find out if there is a poor connection between the alternator and a battery.

There could be two problems with connections:

1. Any of your battery terminals are loose
2. There is corrosion or whitish substance on your terminals.
   

If everything is fine with your connections, the next step is to take the connectors down and check for anything that could prevent electricity from going through. Once your terminals are nice, tight, and free of corrosion, your alternator will charge your battery without a problem.

** Please note that in order to avoid electric shock it is recommended to take down negative connection first and then positive.

If at this point your car is still not starting, you can simply jump-start it and check your alternator as mentioned above. Maybe all you have to do is to use a multimeter to figure out that your battery is actually dead and there was no problem with the alternator.

Faulty wiring and blown fuse could also be a problem with your alternator not working properly. Everything could be fine with your alternator and all you have to do is replace a blown fuse to get it working again!

It may be worth the time just running into the store and getting a multimeter before changing the wrong component of your car! You can use also a voltmeter to check if something is wrong with your alternator.

If nothing works…

Your mechanic probably has all the necessary tools in order to figure out what is wrong with your car. So if your car is “misbehaving” and doing all kinds of weird electrical things, just let professionals do their job (see map below).

This article is for informational purposes ONLY and is NOT a replacement for professional advice!

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