How To Tell if Your Alternator Fuse is Blown

By Jed Lehman •  Updated: 01/30/24 •  5 min read

If your car isn’t starting, one possibility is the alternator fuse has blown. A car’s alternator is a key part of the vehicle’s charging system. It converts engine power into electricity. This electricity powers the car’s electrical components, including headlights, radios, and air conditioners. Staying on top of shorts and blown fuses is a crucial part of car maintenance. In this article, we’ll show you how to tell if your alternator fuse is blown and how to fix it

What is an Alternator Fuse?

how to tell if alternator fuse is blown

Common Amperage Ratings for Alternator Fuses in Various Vehicle Models

Vehicle Make/ModelAlternator Fuse Amperage Rating
Ford Mustang100A
Toyota Camry120A
Honda Civic80A
Chevrolet Silverado150A
Volkswagen Golf90A
BMW 3 Series140A

Note: These amperage ratings are approximate and may vary depending on the specific model year and trim level of the vehicle. Always refer to your vehicle’s owner’s manual or consult a professional for accurate information.

How to Tell if Your Alternator Fuse is Blown

If your car’s engine starts acting up, it could be a sign that the alternator fuse has blown. Here are a few things to look for:

  1. Your engine starts making strange noises.
  2. The engine stalls or doesn’t start at all.
  3. The headlights dim or flicker when the engine is running.
  4. The battery light on the dash comes on.

There are a few more checks you can do to confirm that it is indeed your alternator fuse that has blown.

Fuse Box

Open the hood of your car and locate the fuse box. Inside, there should be a diagram that shows you which fuse corresponds to your alternator. Once you’ve located the fuse, if you notice any discoloration, it has blown.

Continuity

You should replace the fuse with a new one of the same amperage. You can also check the continuity of the fuse using a multimeter. If there is no continuity, the fuse is blown and you need to replace it.

Voltage and Amperage

You can also check the voltage at the alternator output terminal. If the voltage is low, this likely means the alternator fuse has blown. You can also check the amperage draw of the alternator. If the amperage draw is high, this could also indicate that the alternator fuse has blown.

Headlights

The headlights on your car fading or flickering is another indication to watch for. If so, it can mean that the fuse for your alternator has blown. Open your hood and look for the alternator to verify this. A sizable black wire need to connect the battery to the alternator. The fuse has most certainly blown if this wire is slack or has any burns.

Importance of Proper Fuse Ratings

Using the correct amperage rating for alternator fuses is crucial for maintaining the safety and efficiency of your vehicle’s electrical system. Fuses act as protective devices, designed to interrupt the circuit in the event of an overcurrent condition to prevent damage to electrical components or potential fire hazards.

To ensure proper fuse selection, always refer to the vehicle manufacturer’s specifications or consult with a qualified automotive technician when replacing alternator fuses.

How to Replace a Blown Alternator Fuse

If your alternator fuse has blown, it’s important to replace it as soon as possible. A blown alternator fuse can cause your car’s battery to drain, which can lead to all sorts of problems. Fortunately, replacing a blown alternator fuse is a relatively easy task. All you need is a new fuse and a few tools. Here’s how to do it:

  1. Disconnect the negative terminal of your car battery. This will prevent any electrical shorts from happening when you’re working on the fuse.
  2. Locate the blown fuse. It will likely be in the fuse box under the hood of your car.
  3. Remove the blown fuse and replace it with a new one of the same amperage rating.
  4. Reconnect the negative terminal of your car battery.
  5. Start your car and check that everything is working properly. If not, consult a professional mechanic for help.

Alternatives to Replacing a Blown Alternator Fuse

If you think your alternator fuse has blown, there are a few alternatives you can try before replacing it.

First, check the fuse box for any loose fuses. If the fuse box looks fine, then check the wiring to see if anything is loose or damaged. If the wiring looks fine, then you may need to replace the alternator itself.

Another alternative is to check the battery. If the battery is old or damaged, it may be causing the alternator to work harder than it should and blowing the fuse. Try replacing the battery with a new one to see if that fixes the problem.

Conclusion

The alternator is a crucial part of your vehicle’s design. If the fuse that protects the alternator blows, your car will experience electrical problems and will likely cause your engine to not start.

Luckily, this is a relatively easy task that you can do yourself with a few tools and supplies from your local auto parts store. With a little time and effort, you’ll have your car’s alternator working again in no time.

Jed Lehman

Jed Lehman is a born gearhead who has been working on cars since he could crawl. He inherited his love for auto from his grandfather who owned a maintenance shop in Carlsbad, California. Jed is the driver behind Gearshift, and started this site to provide straightforward, helpful automobile information. From maintenance tips to product reviews, you can find it all here.