Is your car showing signs of a failing alternator? Can’t decide whether to hire a professional mechanic or give it a go yourself?

Well, you’ve landed on the right page! You’re about to dive into a well of knowledge about testing your alternator using a simple tool – a screwdriver.

In this guide, we’ll explore:

  • Signs you have a bad alternator
  • A step-by-step process to test an alternator with a screwdriver
  • How to test an alternator using a multimeter
  • The tools required to perform the test
Test alternator with screwdriver

Signs You May Have a Faulty Alternator

Before we encourage you to start using a screwdriver to fiddle about with your alternator, it may be worth knowing the signs of a faulty alternator. After all, no sense in poking about if the alternator is unlikely to be the issue, right?

Some of the more common signs of a faulty alternator include:

1. The Battery is Fully Drained

The alternator has a variety of jobs. One of these is to keep the battery charged while your engine is running.

If your vehicle’s battery is fully drained, this could indicate that the alternator isn’t working correctly.

Remember, an alternator isn’t the only thing that could cause a battery to completely drain. Old batteries (over 5 years old) will struggle to hold a charge. The battery will also drain if the vehicle’s electrics are switched on, but the engine isn’t running.

2. Vehicle Not Starting

Probably the biggest sign of a faulty alternator. If you struggle to start your vehicle (or your vehicle’s electrical systems won’t turn on), then your alternator is probably faulty. Although, this may also be down to a faulty starter or ignition.

3. Electrical Accessories Not Working Correctly

Your alternator provides power to most electrical components in your vehicle. If multiple components stop working, or they don’t work as they should, then the alternator may not be delivering the right amount of power.

If you have electric windows, for instance, you may notice that they start to get slower when you open and close them.

4. Dashboard Lights Not Working

Are dashboard lights flickering or not turning on at all? Could be an issue with the alternator.

5. Vehicle Stalling Frequently

Your engine’s fuel injectors need power. If your alternator is delivering sporadic power, the fuel injectors may not fire correctly. This can cause stalling.

6. Burning Smell Under the Hood

Alternators are prone to overheating. The diodes in them, for instance, can explode. If you notice a burning smell from under your hood, then it could be an alternator.

You’ll probably want to stop your vehicle right away if this happens. A burning smell under the hood is never a good sign.

7. Headlights Dim and Brighten Sporadically

Faulty alternators struggle to give out consistent power. If you notice that your headlights brighten and dim sporadically, this could mean that your alternator is struggling to keep up with the power demands.

Remember, all these problems can be caused by issues that don’t involve the alternator at all. It is just that the alternator is the easiest thing to check if you don’t have proper testing equipment.

Can You Diagnose All Alternator Issues with a Screwdriver?

You can diagnose most, but not all, issues using your screwdriver.

When you test an alternator with your screwdriver, you’re really testing whether the alternator is generating a magnetic field.

As you may know, the job of the alternator is to convert the kinetic energy from the engine to an electrical current. When the electrical current is generated, it passes through a metal coil. As it does this, the metal coil will create a magnetic field.

Using the screwdriver, you’ll be checking whether this magnetic field exists. If it does, the screwdriver will be ‘attracted’ to the alternator. If this happens, it means that ‘something’ is working with the alternator.

What it won’t tell us, however, is whether the alternator is struggling to generate the right amount of power to charge your vehicle’s battery or to power the vehicle’s electrics. If you want to test that, you’ll need a multimeter.

Tools Required to Test Your Alternator with a Screwdriver

You only need two tools for the job:

  • A screwdriver (flat tip is best)
  • A pair of insulated gloves

There must be no rust on the tip of the screwdriver. If there is, find a new one.

The insulated gloves are there to protect you from any shocks. Chances are, you’d be fine without the gloves. But when working on a vehicle it is always better to be safe than sorry!

Testing Your Vehicle’s Alternator with a Screwdriver

Testing your vehicle’s alternator with a screwdriver is dead simple. Just follow these four steps.

Step 1: Pop the Hood

Your first job is to pop the vehicle’s hood. Hopefully, you already know how to do this.

Step 2: Locate the Alternator

Once the hood is popped, look for the alternator. It’ll be bolted onto the side of the engine.

The alternator is normally quite a big component. There’ll be a fan on the back, connected to the drive belt. It is this drive belt that ‘powers’ the alternator, allowing it to generate an electrical current.

You’re looking for a small bolt on the front of the alternator. This is known as the ‘Alternator Pulley Bolt’.

You don’t need to do anything with your screwdriver right now. You’re just locating the alternator. It makes the next couple of steps a bit easier.

If you can’t find your vehicle’s alternator, don’t worry. No matter your vehicle’s model, we’re positive that you’ll find plenty of vehicle guides online. There’ll probably be a YouTube video or two for your specific vehicle.

Step 3: Turn Your Vehicle On

Once you know where your vehicle’s alternator is, head back into the vehicle. Turn the vehicle on. You want the engine to be running. If it isn’t, the alternator won’t work.

Step 4: Hold the Screwdriver Close to the Alternator

With your vehicle switched on, grab your screwdriver and head to the alternator. Be careful here. There’ll be a lot of moving components under the hood now, and you don’t want to jam the screwdriver in the wrong place. You’ll end up with an issue far worse than a damaged alternator.

Hold the screwdriver to the tip of the ‘Alternator Pulley Bolt’. If you feel the screwdriver being pulled toward the alternator, it means that the alternator is generating a magnetic field. This indicates that it is probably working.

Unfortunately, this is about all you can do with a screwdriver. If you still believe there is a problem with your vehicle’s alternator, then get yourself a multimeter. This will allow you to measure the voltage of the alternator. We’ll talk about how to do this in the next section.

Using a Multimeter to Test Your Vehicle’s Alternator

Test alternator with Multimeter

When testing an alternator, a multimeter is a far better option than a screwdriver. As we said, a screwdriver will only tell you whether the alternator is generating power. It won’t tell you how much power it is generating. So, it can’t diagnose all issues.

To test your vehicle’s alternator with a multimeter, follow these instructions:

  1. Switch the multimeter to DC
  2. Switch the multimeter to 20V (or higher).
  3. Turn your vehicle’s engine on.
  4. Touch the multimeter’s red cable to the wire on the back of the alternator (the one that runs to your vehicle’s electrics). Make sure you’re touching exposed metal, not the plastic coating. You can’t test the current if you touch the wire’s coating.
  5. The black cable can touch the top of the alternator. It’s just your ground.

Your multimeter should display a voltage of between 13.5V and 15V. If the alternator is below or above this, then it could indicate that the alternator has a fault.

If you have somebody to help, ask them to turn a few electrical systems on in your vehicle e.g., air conditioning, radio, electric windows, etc. If the alternator’s voltage falls below 13V, then you know that you’ve got an issue with your alternator.

If the multimeter readout is between 13.5V and 15V, your alternator is probably fine. It means that the issue is somewhere else in the vehicle. Unfortunately, diagnosing those issues will be a lot trickier than grabbing a screwdriver or a multimeter, and thus they’re out of the scope of this guide.

Can You Fix a Broken Alternator?

It will depend on the issue. You’ll probably need to be a dab hand at electrical work too. Chances are that if you’ve needed to test your alternator with a screwdriver you probably don’t have the skills, or the equipment, required to fix a broken alternator. Your best bet is to take your vehicle to an auto electrician and have them look at it.

In most cases, your alternator is broken due to one of the following issues: 

  • Damaged wires (maybe shorting, or frayed)
  • Poor lubrication on the bearings
  • Worn bearings.
  • Blown diodes.

All these issues can be fixed easily by a proper auto electrician, and if you have just one or two problems, it shouldn’t cost more than a few hundred dollars.

An alternator with major issues should probably be replaced. Yes. It will set you back a decent chunk of change, but you’ll probably end up saving money in the long run.

A seriously damaged alternator takes a ton of time to repair (this is costly), and often there will be underlying issues that cause it to break repeatedly. At least if you completely replace the alternator, you’ll end up with a warranty on your new component.

Chances are that your future alternator won’t break. They are very robust components, and they should last the life of your vehicle.

Final Thoughts

You can use a screwdriver to test whether your alternator is working. With the vehicle’s engine turned on, hold the screwdriver close to the bolt at the front of the alternator.

If you can feel a magnetic field, then you know the alternator is working. You can use a multimeter to carry out further checks. If your multimeter is broken, find an auto electrician.

Many alternator issues are easy to fix and they don’t always require a complete replacement of the alternator (which can be expensive!).