What Does a Blown 40 Amp Fuse Look Like? (w/ Pictures)

Written by

Charles Bolte


Vernon Hoppe 

what does a blown 40 amp fuse look like

A 40 amp car fuse is critical in protecting the main electrical components in your car. This tiny device is your car circuit board’s first defense against serious malfunctions.

But the 40 amp fuse is also susceptible to damage like any other component. This damage commonly comes in the form of a blown fuse due to a high level of electrical current.

Read this article and know what does a blown 40 amp fuse look like and avoid further problems.

What a Blown 40 Amp Fuse Looks Like


Most 40Amp car fuses today are blade-type fuses. This type is made from metal prongs and slightly transparent plastic material that allows you to see the inside component.

An intact 40Amp car fuse displays no blemishes or burnt smear in any part. The wire bridging the two prongs stays connected and retains its wave-like form.

A bad 40 amp fuse is relatively easy to distinguish, as it remains a tiny, straightforward component. In fact, a burnt car fuse will show a black smear inside, similar to a burnt wire or a plastic.

You will also notice a broken or melted wire inside that’s supposed to connect the two metal prongs. Such wire melts due to the overloaded current.

All these conditions similarly apply to a square fuse, not just to the blade type. A blown jcase fuse, for example, will also exhibit a smear and broken wire connector as you open it from the top.

What Happens if a 40 Amp Fuse Blows


Different scenarios can happen due to a blown fuse in a car, depending on the short circuit’s seriousness or if there are other electrical malfunctions. Such issues can cause minor car device problems or prevent your car from starting immediately.

The most common results of a broken fuse include:

  • Interior and backup lights malfunction
  • Non-responsive turn signal and tail lights
  • Radio problems
  • Air Conditioning control malfunctions

It is not a frequent occurrence, yet your blown fuse can affect your ignition, preventing your car from even starting.

Signs of a Blown 40 Amp Fuse


Aside from the physical traces of a blown fuse, the more noticeable sign is the change in function and performance of internal controls.

Your electrical car components like radio, lighting, power buttons, and climate control will likely show signs of malfunctions.

Also, a broken fuse can affect your speedometer. A blown-out fuse can stop your speedometer from reading your speed and cause other problems in your dashboard– like a flickering check engine light.

For newer model cars, the powertrain, along with its assist and safety features, can also be compromised.

Causes of Blown 40 Amp Fuses


Blown-out fuse is a common issue when you own a car. The inexpensive 40Amp car fuse is supposed to take the fall to protect other major components against short circuits.

However, different factors may cause a fuse to blow. It’s always best to consult professionals should there be more serious electrical problems to uncover.

Here are the common causes of a blown 40Amp fuse:

  • Short circuit
  • Poor wiring
  • Some electrical components malfunctioned
  • Exposure of conductors to moisture
  • Wrongly placed fuse

How to Identify a Blown 40 Amp Fuse

There are a few ways to identify a blown 40Amp fuse; these include:

  1. Diagnose and observe the changes in your car devices’ function and performance. A change in their usual function can signify a blown fuse. A flickering check engine light may also indicate a broken fuse.
  2. Open your car circuit box and physically check the condition of your 40Amp fuse. Check the internal parts to see any physical damage, like a disconnected wire or a burnt smear inside.
  3. To accurately confirm if your fuse is broken, you can check a fuse with a multimeter. Test fuses to determine whether or not a current still passes through or not. A blown one registers a negative or zero reading.

Video Tutorial:

How to Replace a Blown 40 Amp Fuse

Now that you know how to tell what a bad car fuse looks like, it is important that you also learn how to replace one. You can avoid additional costs from a mechanic since you can easily do it yourself.

Before trying to locate your car fuse box, you should turn off your engine and temporarily cut the car’s electrical supply connection as a precautionary measure. Next, follow these steps to replace your blown-out fuse successfully:

Step 1: Secure a new 40 amp fuse replacement


Make sure to purchase a reliable fuse replacement. You can order online or buy in your local auto parts store. One reliable product is the Autozone 40 amp fuse.

It’s important to buy the same type and amperage of the fuse you are replacing.

Step 2: Locate and remove your blown fuse


Fuse boxes are commonly placed under the driver’s side dashboard, near the footwell. Some cars use a second fuse box located under the hood.

Refer to the diagram on the box to find the fuse you need to replace. Cars have several fuses, especially newer models– the diagram on the lid will be your guide. You can take the burnt 40 amp fuse out using pliers.

Step 3: Install your replacement fuse


Push in your new 40 amp fuse following the same orientation as the one you replaced. Make sure to put it tightly and securely to avoid damage and malfunction once you restart your car.

Step 4: Test how your replacement went

You can confirm whether your replacement is a success by checking if there are any signs of electrical malfunctions to your components left. Once the issues are no longer present, you’re good to go.

Video Tutorial:

Tips to Avoid Blowing Out a 40 Amp Fuse

Preventing short circuits in your car is the first defense against a blown fuse. It would be best if you avoid this problem in the beginning. Here are some tips to prevent your car components from short-circuiting:

  • Always pay attention to digital warning signs on your dash and act on them
  • Avoid overloading your electrical system and devices
  • Don’t expose your car too much to heat or water
  • Always maintain proper wiring
  • Avoid using damaged batteries
  • Use 40 amp fuse breaker

Frequently Asked Questions


Can a blown 40 amp fuse be dangerous?

When a fuse is blown, it means it has prevented more costly damage to your major car’s electrical components. A blown fuse cuts the electrical current to a particular component, so it’s not particularly dangerous.

But, it still needs a replacement for the affected device to function again. If the car’s cooling fan fuse is the one that’s blown, it still can be dangerous since this may result in overheating.

How often do 40 amp fuses blow?

The occurrence of fuse blowing depends on the factors that cause your fuse to blow. If you fail to diagnose the reason for the short circuit or your problematic component, you’ll likely experience a blown fuse again.

If your components are usually exposed to moisture, chances are high that you’ll also experience blown fuses more than usual.

How much is the cost to replace a 40 amp fuse?

A 40 amp car fuse cost is relatively cheap. Blade-type and cartridge-type fuses of the same amperage can cost around $1 to $1.5 US if you purchase online. The price will vary from different physical stores.


40 amp car fuses protect the major electrical components of a car, so, normally, you’ll experience a broken fuse. This inexpensive device saves you from further damage costs, so make sure you always have them in place.

Now that you are aware of what does a blown 40 amp fuse look like, it would be easier for you to diagnose your car’s electrical problems. Replacing a burnt car fuse will be easy with this guide in mind.

Read more: Ways to identify a 30 amp fuse blown

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