How to Test the Alternator Field with a Screwdriver

When your car battery fails, you might think it’s the battery that’s the issue. However, the battery might be just fine, but your alternator could be causing the problem. The alternator is responsible for charging your car’s battery, and if it’s not working correctly, your car will eventually fail to start. In such cases, it’s recommended to check the alternator’s field.

But, how do you do that? In this DIY guide, we’ll show you how to test the alternator field with just a screwdriver.

Step 1: Preparing the Screwdriver

Before you proceed to test the field, prepare the screwdriver you’ll be using. Take a flathead screwdriver, and wrap some electrical tape around its metal tip. This is to prevent you from grounding the screwdriver during the test, which can result in electrical hazards.

Step 2: Locating the Alternator

Once you have your screwdriver, locate your alternator. Typically, it’s found near the engine’s front. Identify the two terminals attached to the back of the alternator. One is connected to a thick cable that runs to your car’s battery, while the other is connected to a control wire, which usually has a plastic connector. Note: It’s essential to verify your alternator’s terminals by consulting your car’s user manual. Different car models might have varying locations of the alternator and its terminals.

Step 3: Testing the Field

Insert the tip of your screwdriver inside the plastic connector (control wire) attached to the alternator’s terminal. While doing this, make sure that you hold the screwdriver by its plastic handle, and not by the tape. Once you’re in, check to see if there’s a magnetic pull on the screwdriver. If there is, your alternator field is working correctly. If not, there could be a fault with the field, and further inspection is necessary.

Step 4: Checking Other Alternator Components

Now that you have verified the field’s functionality, you may still be experiencing issues with your car. This could be due to other alternator components, such as diodes or voltage regulators, that have gone bad. So, you might require additional checks on the other car components to determine the exact issue.

Step 5: Seeking Professional Help

If you’ve completed the above steps and still have no clue what the problem is, it’s best to seek a professional’s assistance. A qualified mechanic will have the necessary experience and equipment to check the alternator thoroughly and determine the issue before it becomes worse.


Testing the alternator with a screwdriver is an easy and affordable process. By following the steps outlined above, you can determine whether the alternator field is causing the issue. At worst, the screwdriver test will reduce some of the guesswork involved before seeking professional help. However, if the problem persists, don’t hesitate to ask for a certified mechanic’s help.

Remember, regular battery checkups and maintenance might help avoid such problems in the future. It’s always better to detect issues early and save yourself some time and money later on.

Ronald Cantrell

My name is Ronald and I'm a passionate home tools blogger who loves to help people find the perfect tools for their homes. I'm constantly on the lookout for the latest and greatest products so people can make informed decisions when it comes to their DIY projects. In my spare time, I like to tinker around with projects of my own and put my knowledge of tools to the test.

Click Here to Leave a Comment Below 0 comments