Replacing a Blown Automotive Fuse

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Thar She Blows, Darn Fuse!

Benjamin Chun/Flickr

If you're driving at night and all of a sudden find yourself navigating by moonlight, the last thing you want is to be stranded in the dark. Luckily you're in the Automotive Empowerment Zone and you know how to fix things when they go awry.

So your headlights are out. Chances are it's not a bulb since you just replaced your headlight bulb last week. Besides, what are the chances of both bulbs going at the same time? It's time to check the fusebox to see if anything blew.

There are actually three types of automotive fuse: ceramic, glass tube or blade. If your car was made before, say 1980 or so, you probably have the ceramic or tube style fuses. These are actually available in either the very old glass tube, or the slightly more modern plastic mount. Both of these are shaped like a small torpedo and are easy to install. The other type, and the kind of fuse you most likely have in your car, is the blade style. These plug into your fusebox just like a wall plug. Check to see what type of fuse you have so that you can keep a few spares around. Now that we have some fuses, where do we stick 'em?

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Under the Dashboard Fuse Box

Check the handy fuse diagram.
Most cars have a fuse box under the dash. Matt Wright

These days many cars have two locations for fuses. I'm not sure what the reasoning is, but they do it. It does keep things a little less cluttered.

Whether your car has one fuse box or two, it will have one underneath the dashboard. It is usually located just in front of your left knee if you're sitting in the driver's seat. We recommend using your hand to replace the fuse as it will take much longer using your knee. The fuses will be hidden behind a plastic cover, but it's usually marked clearly. Open the cover and you should see a row of different colored fuses sitting nicely inside. You will also probably (hopefully) find a diagram on the cover that shows you which fuse goes to what.

Most cars even provide some spare fuses and a little fuse puller that you can use to remove a blown fuse and insert a new one. In the case of your headlights being out, find the slot on the diagram that indicates the headlight fuse. Grab it with the fuse puller (or our fingers if you have no puller) and pull it out. If it's blown, you'll see a melted "bridge" going between the two blades. Trust me, you'll know if it's blown. If it's not blown, and you know you have located the right fuse, you'll need to either get down to electrical analysis or take your car in for repairs.

Find a new fuse in your spares, or if you have no spares get it from the spares you bought. Be sure to use the same amperage fuse. They are both color coded and imprinted according to amperage, so if you install the same color fuse you're golden.

But there's no headlight fuse on the diagram!

Don't fret. If you don't see the fuse you're looking for under the dash, you probably have a second fuse box under the hood. Read on.

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Under the Hood Fuse Box

Outside fuse box.
2nd fuse box under the hood. Matt Wright

Many cars these days have a second fuse box under the hood. It's usually very easy to find and get to, with a nice diagram on the top telling you what fuses are inside. In addition to the regular blade type fuses, you might also see some really big fuses that protect your car's entire electrical system.

The procedure for replacing a fuse under the hood is the same as under the dash. Find the fuse that's blown, pull it out, install a new one. Now put the cover back on and let there be light, or stereo, or turn signals.