How to Test the Alternator with a Voltmeter, Screwdriver & Multimeter

Sharing is caring!

Last updated on August 1st, 2023 at 07:43 am

Are you wondering if your alternator is in order? Well, if you like to see how to test the alternator on a car using a Voltmeter, Screwdriver, or even a Multimeter, we have got you covered. Sometimes, it’s very difficult to say, especially if you do not know what to look out for.

However, the best method to check is by using a voltmeter, which is why we will show you how to test the alternator with a voltmeter. What Kills An Alternator

How to Test the Alternator on a Car Using Either Screwdriver, Voltmeter or a Multimeter

We will also consider the following subtopics on the alternator how-to test  and all related questions below:

• How to find alternator amperage, how to test the alternator with a screwdriver, how to test the alternator with a multimeter, what need when testing the alternator amp output with a multimeter, how to test an alternator by disconnecting the battery, and finally, how to check an alternator by disconnecting the battery. So stay tuned.

So you have a new battery and recently changed your car batteries, and yet your vehicle could not start? Then, it is most likely that your alternator is bad.

Today, we will share with you how to test the alternator with a voltmeter. Below are the steps to follow :

Related Article: Can A Car Run With A Bad Alternator (Risks Of Driving With A Bad Alternator)

How to Test the Alternator with a Voltmeter

• Connect your meter leads via battery terminals by looking for 13.8 to 15.3 volts.
• Please, you shouldn’t disconnect the negative battery cable just to test an alternator. If there is no battery in the circuit to act as a buffer, it simply means the alternator will produce up to 150 volts, which depends on your engine AMPs.
• It would help if you bought a voltmeter instead of disconnecting your battery cable. Then put off your engine, and set your battery voltage at 12.5 to 12.8 volts. Note that if your battery is lower than that, it must be charged first. And after which, turn on your engine and observe an increase in voltage reading, then if there is an increase in reading, it means the alternator is in perfect condition.

Also, Read this:

How long does it take to fully charge a Tesla+ Tesla Battery Replacement Cost

HOW TO FIND ALTERNATOR AMPERAGE

The word amperage (AMP) happens to be a word used to describe the rate at which electric current flows. One of the best ways to know the problems of the alternator is to examine the base and have an idea of the AMP the alternator generates.

For you to know how to find alternator amperage, you need to have an understanding of how AMPs and volts work. AMPs are known to be the current’s power, while volts are the capacities of any current.

To know an alternator’s amperage, you should note that alternators of bigger vehicles are likely to increase the amperage output, which is around 200 to 350 AMPs. At the same time, small vehicles produce around 100 AMPs with a battery that runs on 12 volts.

You can examine the fuse rate of your vehicle’s electric components; then, you can calculate the AMP your alternator runs on. Alternatively, check for a diagram on your fuse cover, you will see the AMPs numbers your manufacturers have set, just sum the numbers, and you will know the AMP the alternator requires to power your vehicle’s electric components.

HOW TO TEST ALTERNATOR WITH SCREWDRIVER

If you want to learn how to test an alternator with a screwdriver, then follow these steps:

• Please insert the vehicle key on the ignition switch without starting the engine.
• Before accessing the alternator, open the vehicle’s hood so you can test the alternator current.
• You are to test the magnetism of the alternator, so put the metal screwdriver close to the bolt on the alternator pulley.
• You can then turn the key of your car to the on position without starting the car. This will activate the voltage regulator, put the metal side of your screwdriver close to the nut on the alternator’s pulley; you will observe a high magnetism which should pull the screwdriver. If this happens, it means the alternator is working perfectly, but if it didn’t, it means your alternator is not working perfectly. What Kills An Alternator +Guide On How To Clean Alternator

How to test an alternator with a multimeter

Before you will test the alternator with a multimeter, ensure your car battery is completely charged. Then remove the negative lead from the multimeter and place it on the negative post of the car battery. After which, insert the meter’s positive lead on the battery positive lead, set the meter to DC voltage, use 20 scales, and then observe the display to ensure the battery is completely charged.

You can then start your car to find out what your alternator is generating. Note that reading should increase, but if not, it means your alternator is not generating current. You can now turn on your heater blower and light to examine, if the alternator is not strong enough, then allow your vehicle to run for some time, and once it reads, it means your alternator is in perfect condition.

TESTING ALTERNATOR AMP OUTPUT WITH MULTMETER

• Examine the AMPs the alternator generates if it works perfectly. Then examine the specification are of your vehicle’s manual, where you will see alternator details. This will inform you about the maximum/minimum AMP of your alternator. Note that the maximum is anytime you put on something that consumes energy in your car, while the minimum is when you put on something like a car stereo. So ensure you write them down for record purposes because you will need them again.
• You will need to get closer to your vehicle’s battery so you can examine the AMP output via the alternator, but first, ensure you put on your glove.
• After which, open your vehicle’s hood, start the engine, and allow it to idle for some time. Please ensure nothing consumes energy, like car air condition or light, because you need to examine the minimum alternator AMP output.
• You can now bring out your multimeter, set it to read the AMP. Now insert the metal on the ending side of the black wire, which extends the multimeter to the negative battery terminal. Note that this negative battery terminal comes with a black cable which is labeled NEG. Place the other metal on the ending side of the red wire on the positive battery terminal. Note that the positive terminal comes with a red cable which is labeled POS.
• Examine the multimeter; it should be reading the minimum AMP you jotted down before. Though it does not matter if it’s 10% higher or lower than the minimum specification, if it’s 10% lower, then get an expert to examine the alternator. And if it’s 10% higher, examine to ensure you didn’t turn on any electric component, and if you didn’t, then contact an expert for help.
• Put on the energy-consuming components like your air conditioner, light, and wiper. This will increase the AMP because they are components that consume energy. Then your alternator will adjust the output, that is if the alternator is working well.
• Try to measure the alternator AMP output making use of the multimeter as you did before. Note that the reading will be near the maximum AMP you wrote down earlier. In case, the reading is 15% lower than the maximum, ensure you turn on as many components as possible. And if you did, then examine your alternator. But if you didn’t turn on many components, then do so and examine the reading again. After which, if you observe little or no change, then contact an expert to examine your alternator.

Once done, you can now turn off your car and close the hood.

Related Article: How to Start a Car with a Bad star& broken starter with a screwdriver

How Many Volts Are Car Batteries? (Car Battery How Many Volts)

Sharing is caring!