Let’s face it: Accidents happen. Minimizing the collateral damage from an accident is important. When you have a mobile electronics system that includes installing an amplifier in your vehicle, a discussion about fuses or circuit protection should take place before the installation begins. Choosing the right device to ensure your system works as intended and is safe in the event something goes wrong is very important. Let’s talk about fuses.

What is a Fuse?

A fuse is a device that will disconnect a circuit when too much current passes through it. Fuses typically incorporate a small piece of metal with a specific amount of resistance. As current passes through the fuse, the piece of metal heats up. Up to a certain temperature, the circuit remains functional. If the current level increases, the fuse heats up more and will eventually fail, which protects the power source and load.

My Wire Needs a Fuse?

Two common locations in our audio systems need protection. Any power connection to the battery needs a fuse. Any electronic device connected to the vehicle electrical system should also have a fuse.

The fuse at the battery is there to protect the vehicle in the event of a short circuit. If it is installed incorrectly, the power wire may rub against a sharp object and wear through the jacket. Once the conductor touches the chassis, a short circuit will occur. Left unprotected, the only limiting factors in how much current passes is the internal resistance of the battery, the resistance of the power wire and the resistance of the connection to the chassis. In most cases, hundreds of amps of current will flow – if we don’t have a fuse on the battery.

Imagine a car with a big stereo system. There may be an upgraded AGM battery under the hood and a few huge amplifiers in the trunk. What if the unthinkable happens – the car is involved in an accident, and the chassis shorts to the power wire? Without a fuse on the power wire connection to the battery, both the wire and the battery will heat up very quickly and could easily start a fire.

Fuses in Our Devices

Recently, we experienced an instance where a radio was blowing the 15 amp fuse in its power harness as soon as it was plugged in. Even with all the speakers disconnected, it kept blowing fuses. It turned out there was an improperly soldered terminal on the internal amplifier in the radio. This poorly soldered connection was shorting the power connection to the chassis of the radio and, subsequently, to the ground. The 15 amp fuse in the harness prevented the copper traces on the circuit board from being destroyed. Our technician was able to clean up the solder connection, and we put the radio back into service.

Types of Fuses in Car Audio

More and more new fuses are introduced to automobiles each year as manufacturers strive to reduce weight and packaging sizes. On the aftermarket side, we use three common fuse styles.

AGC and AGU Fuses

AGC and AGU fuses are constructed from four components: a fusible link, a pair of end caps and a glass tube. The manufacturer solders the fusible link to one end cap, then slides the glass tube over the link before soldering on the other end cap. Many radio harnesses and lower-power devices use AGC fuses. For years, the larger-diameter AGU fuses were very popular in amplifier installation kits.

The problem with these fuses is that the quality and reliability of the internal solder connections can affect their performance. We have seen brand-new fuses out of package not work because the solder connection on one cap was incomplete.

Another consideration for AGC and AGU glass fuses is how we connect them to our power wire. In most cases, a terminal is pressed against the end cap using a sprung metal connection. As this connection heats up, it can loosen. For low-current applications, AGC fuses are acceptable. For moderate- to high-current applications, there are better alternatives.

ATC, ATM and Maxi Fuses

This style of fuse is composed of two components: a plastic housing and a stamped metal piece that includes the electrical connection tabs and current-limiting link. These fuses are compact and easy to install. They eliminate the connection that plagues the glass fuses, but they still suffer from problems when it comes to connecting them to the power wire. In almost all applications, sprung metal tabs are responsible for pressing the tabs of the fuse against the wire terminals. These can fail over time.

A common point of failure is the loop-type under-hood fuse holder that are included with aftermarket lighting kits. These molded holders include two female terminals connected to the input and output wire. After time and many heat cycles, these terminals can loosen, and the resulting resistance will cause the holder to fail. It should be noted that the current required to heat up the connection to the failing point is often less than what is required to blow a fuse.

ANL and Mini-ANL Fuses

In the mobile electronics industry, ANL and Mini-ANL fuses are the preferred option when it comes to protecting devices from over-current conditions. These fuses are constructed in the same way as an ATC, ATM or maxi fuse, with a single metal plate that is stamped to provide the connection terminals and the fusible link. A plastic housing snaps over or rivets to the device to enclose the link.

Where these fuses differ from the other two styles is in how they are connected to the wiring. A set of large blocks connects to the wire. Most of these blocks use set screws. The fuse is then attached to these blocks with a large-diameter bolt. Your installer can (and should) tighten the bolt to ensure that the electrical connection is solid and secure.

Protect Your Vehicle and Equipment

Whenever you have your installer adds an electrical device to your vehicle, it must be fused. Even a small-diameter wire for an auxiliary USB charge port, a radar detector or LED lighting can cause an impressive amount of damage when overheated. It will not only melt through its jacket, but will melt the wiring around it. Proper circuit protection is cheap insurance against having to call the insurance company. Your local mobile electronics specialist retailer would be more than happy to discuss how and where they fuse the equipment they install.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

When you go shopping for a new radio for your car, one of the many questions the product specialist should ask you is whether your existing radio has steering wheel-mounted audio controls. Almost every aftermarket radio has provisions to accept a signal that will give you steering wheel audio control functions like volume, source selection, tracking and power. Here’s how it all works.

Factory Control Functionality

There are two common types of steering wheel control interfaces. The first is resistive; the second is data. Systems that use resistors often have two wires connected to the switches. Each switch presents a different resistance value when pressed. The factory radio sees these different resistances as different voltages and the computer in the radio responds appropriately. There are usually two wires so a multitude of switches can have well-separated resistance values to ensure functions will never overlap.

A small computer is built into the steering wheel controls switches in vehicles that use data communication for the steering wheel audio controls. This computer has inputs dedicated to each switch and its function. When you press a switch on the steering wheel, the computer sends a digital communication to the computer in the radio. Often, this communication takes place on the vehicle’s CAN data network.

Connection to Aftermarket Radios

In North America, almost every radio is Steering Wheel Remote Control Ready. Being “Ready” means the radio has a connection on the back to accept a serial data communication signal. The communication language used on the radio connection is not the same as that used in the vehicle. Thus, you will require an interface module to make everything work. Companies like iDatalink, Axxess and Pacific Accessory Corporation (known in the industry as PAC) all offer interfaces that can be programmed to understand and translate the information from the vehicle to something that is compatible with your radio.

Steering Wheel Audio Control Installation

When your tech is installing the new radio in your vehicle, he has three tasks to complete to make the steering wheel audio controls work. First, he must wire the controls into your vehicle. In many cases, the installer will use a “harness saver” or “wire harness adapter” to connect a set of bare wires to the factory radio plug for power, illumination and speaker wire connections. This adapter usually includes the steering wheel communication wires from the vehicle.

Once the installer completes the electrical connections, the next step is to program the module to understand the commands from the vehicle. Some interfaces have software built into them to recognize commands from the vehicle automatically.

Another method of programming the interfaces uses a website that will allow the installer to select the year, make, model and trim level of the vehicle, and program the interface to recognize the correct commands.

Finally, the interface has to be programmed to send the correct commands to the new radio. Each brand of radio has a set of dedicated and unique command codes.

Additional Options

Over the past few years, many vehicle owners have chosen to upgrade their factory radios to add Bluetooth audio streaming and hands-free calling to their vehicle. New cars have telephone control buttons on the steering wheel, but older ones don’t. Several of the interface modules have the ability to send different commands to the aftermarket radio, depending on how long you press and hold the steering wheel buttons. For example, a quick tap on the Volume Down button will, of course, turn the volume of the aftermarket radio down. You can have the button programmed so pressing and holding it for a couple of seconds to tell the radio to answer an incoming Bluetooth phone call.

The list of compatible functions varies by vehicle and the make and model of the aftermarket radio.

Custom Applications

One unique feature of the steering wheel control interface is that your installer could build a set of custom controls for you. Let’s say you are building a custom car, and you want to add a nice sound system. In most applications like this, the builder will install the aftermarket radio in the glovebox, under the seat or in the trunk of the vehicle. But how can you control the radio if you cannot reach the controls? Your installer could mount a set of switches in the center console and then program the switches, through an interface module to control the aftermarket radio.

Some installers and fabricators have gotten quite creative with these switch installations. A power mirror adjustment switch, for instance, serves as a great solution for volume and tracking functions.

Your Retailer is Ready to Help

When it is time to install a new radio in your vehicle, drop by your local mobile electronics specialist retailer. They would be happy to show you the latest in car audio source units and explain how they can integrate it into your vehicle.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.