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How to Replace a Blown Fuse in Your Car

By Mia Bevacqua, May 17, 2018

Your car is filled with electrical wiring and circuits. So, when something goes wrong — whether it’s a window that won’t go down, a brake light that stops working or even a problem starting the car — it’s usually worth checking to make sure that a fuse hasn’t blown.


Image courtesy of Wikipedia/Michiel1972

If a fuse has gone bad, it’s pretty easy to replace. But it’s important to try to find the root problem before installing a new fuse — otherwise, the replacement will blow, too. This might involve a trip to your mechanic for an inspection.

Let’s look at what fuses do, or you can jump ahead to learn how to find the right one when you need to, how to take it out, how to tell if it’s blown, and how to swap it out for a new one.

What fuses do

Fuses protect circuits from getting overwhelmed with electricity. If too much current flows through the fuse, it “blows.” This prevents the rest of the wiring and electrical components from getting damaged.

Each individual fuse is labeled with an amperage rating, which indicates the amount of current needed to cause it to blow. Inside the fuse, there’s a small strip of metal conductor that melts when that threshold is exceeded. The thickness of the strip determines the fuse’s rating.

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How to locate a fuse

Most modern vehicles use blade-style fuses. With this design, the fuse’s metal conductor strip is encased in a plastic housing. The strip connects between two metal blades that extend from the housing. 

Blade-style fuses are located in a fuse box or electrical distribution block. Typically, there is one box under the dash on the driver’s side, and another under the hood. The exact location of these boxes can be found in your owner’s manual

Fuse boxes hold dozens of fuses. In most cases, there’s a legend attached to the box lid for identifying an individual fuse. The owner’s manual will also have this information. 

How to remove a fuse

After you’ve located the correct fuse, you’ll need to remove it. This is easy to do — simply pull the fuse straight out of the box toward you. In many cases, you can do this by gripping the fuse with your fingers. 

If that doesn’t work, a fuse puller (some vehicles have one attached to the fuse box) or a pair of needle-nose pliers can be used. Be careful not to squeeze the fuse too tightly if you use pliers.

How to diagnose a blown fuse

Fuses blow for a reason. It could be a short circuit or faulty component causing the problem. After you’ve removed the fuse, look inside the fuse to see if the metal strip is melted in the middle. You may also see char marks. If you see either of these, the fuse is blown and will need to be replaced.

Another, more advanced way to test a fuse is with a digital multimeter. Turn the meter to the ohms setting, then attach one lead to each of the fuse blades. The meter should display a numeric reading. If it displays “OL” (out of limits) instead, the fuse is blown and will need to be replaced.

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How to install a new fuse

The first step is to make sure you select the proper replacement fuse. DO NOT install a fuse with a different rating than the original fuse — doing so may prevent the fuse from blowing when the circuit is overloaded. This can result in extensive circuit damage and even a fire.

Once you have the correct fuse in hand, gently push it into its slot in the fuse box. Check the circuit to make sure it’s operating properly. Remember, a blown fuse indicates a circuit problem that must be addressed. Otherwise, any replacement fuses will continue to blow.

 

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