How Does a Car Fusebox Work?

by John DeCostanza

Identification and Location

Under the hood: Fusebox and cover

There is always at least one fusebox on a car, but there are often more than one, in multiple locations. The most common location for the fusebox, or fuseblock inside the passenger's compartment, is under the dashboard, roughly at the driver's left knee. Other locations can include inside the glove compartment or under the dashboard in another location. The boxes are labeled "Fuses" on the plastic cover, which has a handle molded into it. The other fuseboxes are under the hood of the car, and are about 4 inches wide and 8 inches long. They are usually placed in accessible locations and covered tightly to protect them from moisture. They may be marked "Relay" or "Power Distribution Center."

The Fusebox: Home of the Protective Fuse

The fusebox is just that: A box that holds fuses that ward off an overload to various electrically powered systems and accessories in a car. Think of the fusebox as a sort of clearing house for the electrical system of the car. By placing fuses in the box as part of the electrical circuit for, let's say, the windshield wipers, the engineers are protecting the motor that drives the wipers from burning up under stress. The fuse that sits in the fusebox is essentially no different than a piece of wire with current passing through it. But when the wiper blades are frozen to the windshield and the motor strains to break loose from the ice, thus drawing too much amperage, the fuse is designed to blow before the wiper motor burns up.

What You Might Find in a Fusebox

Cover, diagram, tool and spare fuses

Fuseboxes are always covered to prevent moisture damage and inadvertent dislodging of the fuses. There is always a diagram that illustrates where each fuse is located, what its amperage is and what it controls. This is usually found on the inside of the cover. (This information is also available in the owner's manual.) Many fuseboxes have a dedicated slot to hold a tool with which to remove fuses, because many mini-fuses are difficult to remove with your fingers. Spare fuses are also sometimes kept in the fusebox. Flashers that cause the hazard lights and turn signals to light intermittently may be found here as well. Fuseboxes located under the hood may also contain relays that help operate integral parts of the cooling and fuel-supply systems.

About the Author

John DeCostanza has owned an auto repair facility for over 35 years. He is an ASE certified service consultant and auto parts specialist. He has been writing as a freelancer since the late 80s. His writing credits include a Gannett newspaper and " Newsweek"  magazine. DeCostanza is a graduate of the University of Delaware where he earned a Bachelor of Arts in English.

Photo Credits

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