Do I Need a Car Amp Fuse?

Choosing the right size and location

Most cars come with basic audio systems that include only a head unit and four speakers, so upgrading beyond that is more complicated than simply replacing old components with new ones. If your car didn't come from the factory with an amplifier, and it probably didn't, you need to wire it into power and ground. That means you need some type of amplifier fuse.

Car amp fuse

Andy Arthur / CC by 2.0 / Flickr

Who Needs a Car Audio Amplifier Fuse?

If your new power amp came with a built-in fuse, it's meant to protect the amp itself; it won't do anything to protect the rest of the wiring in your car. Of particular concern is the amplifier's power wire, which could short out somewhere down the line.

If you aren't careful when running a power wire for your new amp, it shorts out and it isn't fused, and you could be looking at significant damage. In a worst-case scenario, a shorted-out amp power wire could cause a fire.

Even if you're careful, simply driving around on the smoothest of roads jostles everything in your car around. Over time, wires shift and abrade against each other and other things. That's why the fuse is one of the most vital parts of amp wiring.

Connecting Your Amp to Power

Resist the urge to hook up your new amp to the existing fuse box in your car or to an existing circuit or fuse. Your amp is almost certainly going to draw more amperage than the existing wiring is designed to carry. That means you're risking catastrophic failure, even if you swap out a smaller fuse for a bigger one or use an empty slot in the fuse box.

The issue is closely tied into the way fuses work and the problem they're designed to take care of. In the most basic terms, a fuse is designed to fail. If any component in the circuit draws too much amperage, or a short circuit results in a sudden amperage spike, the fuse will blow and interrupt the circuit.

If no fuse is present, or the fuse fails to break the circuit because of arcing, other components can be damaged. An electrical fire could result.

Proper Car Amp Fuse Location

Since car audio amplifiers draw a lot of amperage, wiring one improperly can result in overloaded power wires, shorts, and even electrical fires. That's why it's a good idea to run a separate power wire all the way from your battery to your amp.

If you have multiple amps, you can run a single power wire and use a distribution block, but the power cable has to be thick enough to handle the current draw from all of the amps that it feeds.

If there is ever an issue with one of your amps, or your amp power cable shorts out, the results could be potentially catastrophic. In the worst-case scenario, the car could catch on fire or the battery could explode.

That's why it's necessary to install an in-line fuse between the battery and the power cable, and it's also why you should place that fuse at the battery instead of at the amp. If you place the fuse at the amp, and the cable shorts out somewhere between the battery and the fuse, the fuse won't provide any protection at all.

Proper Fuse Size

If you use a fuse that's too small, it will blow during normal operation. If you use a fuse that's too big, you could end up with component failure or an electrical fire.

If your amplifier has an internal fuse, your inline car amp fuse should be a bit larger. For example, use a 25- or 30-amp inline fuse if your amp has an internal 20-amp fuse.

If you have two amps with internal fuses, add the amperage ratings together to figure out the right size for your inline fuse. That gives you wiggle room without risking a dangerous situation.

Some amplifiers don't have internal fuses. In this case, check your amp's power ratings to determine the proper size fuse.

If your amp doesn't have an internal fuse, or you have multiple amps without built-in fuses, consider using a fused distribution block. In the same way that the inline fuse protects against a shorted-out power wire, a fused distribution block protects your other amps and related components if one of your amps fails.

Types of Fuses for Amps

Most amplifiers with internal fuses use automotive fuses. These are the same type of fuses used elsewhere in your car; other audio components, like the head unit, might use similar fuses.

When you install an inline fuse, you can use this same type of blade fuse. The fuse itself is installed in a fuse holder, which you connect inline with the amp power line.

The other option is to use an inline barrel fuse. This also uses a fuse holder that you install inline with the power wire, but it typically takes the form of a clear or translucent plastic tube that holds a barrel fuse.

Regardless of the type of fuse, it's important to select a fuse holder that meets or exceeds the rating of the fuse you plan to install. If you determine that you need a 30-amp inline fuse, don't install a fuse holder that's rated for only 25 amps.

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