Most cars come with very basic audio systems that only include 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 amp, and it probably didn’t, that means you need to connect it to power and ground, and that means you need some sort of fuse for the amp.
Who needs a fuse for car audio amplifier?
If your new power amp comes with a built-in fuse, that’s great. However, that fuse is meant to protect the amp itself, and will do nothing to protect the rest of your car’s wiring. Of particular concern is the amplifier’s power cable itself, which could short-circuit somewhere along the line.
If you’re not careful when you run a power cable for your new amp, and it cuts, and isn’t fused, you could be looking at significant damage. In the worst case, a short circuit in the amplifier’s power cable could even cause a fire.
Even if you’re careful, just driving on the smoothest of roads causes everything in your car to wobble and push through a lot of terrain. Cables shift over time and wear against each other and other things, which can cause even the best laid plans to go awry. This is why the fuse is one of the most vital parts of the amplifier wiring.
Connecting your amplifier to power
It can be tempting to connect your new amp to your car’s existing fuse box, especially if the fuse block is located under the dashboard. It’s certainly easier than running a whole new power cable to the battery, but resist the urge to take this shortcut.
The reason you should avoid connecting an amp to the fuse box inside your car, and especially never connecting it to an existing circuit or fuse, is that your amp is almost certainly going to draw more amperage than your wiring harness. fuse box is designed to carry.
This means you risk a potentially catastrophic failure, even if you swap out a smaller fuse for a larger one, or use an empty slot in your fuse box.
The topic at hand is closely related to the way fuses work and the problem they are designed for. In more basic terms, a fuse is a component that is designed to fail in order to protect everything else in the circuit. If any component in the circuit draws too much amperage, or a short circuit results in a sudden increase in amperage, the fuse will “blow” and break the circuit.
If no fuse is present, or if the fuse fails to break the circuit due to arcing, then other components may be damaged, or there may even be an electrical fire.
The correct location of car amplifier fuses
Because car audio amplifiers draw a lot of amperage, improper wiring of one of them can result in overloaded power cords, short circuits, and even electrical fires. That’s why it’s a good idea to run a separate power cable from the battery to the amp.
If you have multiple amps, you can use a single feeder cable and distribution block, but the feeder cable needs to be thick enough to handle the current draw of all the amps it feeds.
If there is ever a problem with one of your amps, or if your amp’s power cable cuts, the results could be potentially catastrophic. In the worst case, the car could catch fire or even the battery could explode.
This is why you need to install an in-line fuse between the battery and the power cable, and also why you should put that fuse on the battery instead of the amp. If you put the fuse in the amp and the wire breaks somewhere between the battery and the fuse, then the fuse will not provide any protection.
The correct size of the car amplifier fuse
In addition to placing the fuse in the proper location, it is also important to use the proper size fuse. If you use a fuse that is too small, it will blow during normal operation. On the other hand, if you use a fuse that is too large, you could end up facing component failure or an electrical fire.
If your amp has an internal fuse, then the car amp’s inline fuse should be slightly larger. For example, you may want to use a 25 or 30 amp in-line fuse if your amplifier has an internal 20 amp fuse.
If you have two amps that have internal 20 amp fuses, then you need to add those numbers together to find the correct size for your inline fuse. That gives you a bit of wiggle room without opening yourself up to a dangerous situation.
Some amps don’t have internal fuses, in which case you’ll need to check your amp’s power rating to determine the proper size car fuse.
If you’re dealing with one amp that doesn’t have an internal fuse, or even multiple amps that don’t have built-in fuses, you should also consider using a fused distribution block. In the same way that the in-line fuse protects you from a shorted power cord, a fused distribution block will protect your other amplifiers and related components if one of your amplifiers fails.
Types of fuses for amps
Most amplifiers that have internal fuses use some type of automotive fuse. These are the same type of fuses that are used in other parts of the car, and other audio components such as the head unit can also use very similar fuses.
When an in-line fuse is installed, this same type of fuse can be used. The fuse itself is installed in a fuse holder, which is connected in line with the power line of the amplifier.
The other option is to use an in-line fuse. This also uses a fuse holder that is installed in-line with the power cord, but typically takes the form of a clear or translucent plastic tube that holds a barrel-shaped fuse.
Regardless of the type of fuse you use, it is 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 in-line fuse, do not install a holder that is only rated for 25 amps.