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How to Make a Car Stereo Wiring Harness?

Sometimes, when installing your new car stereo, you may need a bit of modification, especially when your new car stereo harness is not compatible with your current car’s harness. But how to make a car stereo wiring harness? Let’s find out.

To make a car stereo harness, you may need to either use the existing harness or make a completely new one from scratch, considering wiring diagrams and wire selection. Also, you need to cut and join wires together. In some cases, remove both car and stereo harnesses, and make small connection terminals. 

As an Amazon Associate, ImproveCarAudio will receive a small commission from qualifying purchases made through the links in this article.

Tip: Making a harness allows you to customize a car stereo, especially when you do not have the original one together with the stereo.

Not all of us however, feel comfortable playing with the wires. If you are one of the persons that would prefer to purchase a replacement for your original harness, click this link and check the harnesses for car stereos on Amazon now. 

If you think that making your own wiring harness for a car stereo is difficult, then you do not have to worry too much because it is relatively simple, although time-consuming. 

In this article, I will highlight all the pros, and cons, and I hope all questions you may have relating to making your own car stereo harness.

What Is a Harness for a Car Stereo?

A stereo harness is also known as a wiring harness, wire harness, wiring assembly, or wiring loom. It gathers and joins wires (electrical cables) that will relay an electrical signal or power.

how to make a car radio wiring harness

 All wires are typically bound together by non-conductive material such as rubber, electrical tape, and vinyl. They are connected to a little plastic device (connector or terminal) at each wire’s ends, doubling as a push-pull switch when the device is connected to its counterpart. 

As with most audio connection points (terminals), you will typically have a female and male connector. The male connection point is the connection that must be inserted, and the female connection is the connection point that will receive the male connection point. This is apparent in any audio and video cables that you get.

The same is true for a wire harness (at least for the plastic connection). Furthermore, even though a wiring harness is typical and standard in most vehicles and most car stereos, they are not all the same.

In reality, the design and number of wires will be the same for all wiring harnesses. However, many will be visually different. 

Advantages of a wiring harness

If you are dealing with some part of a car audio system and find yourself in a situation without a wiring harness, this could be frustrating because a wiring harness has a few important advantages. 

Reduced installation time

Every vehicle to operate correctly requires many meters of wiring. A wiring harness dramatically simplifies manufacturing devices and cars by combining all the wires into one terminal.

Consequently, installing other vehicle components becomes more effortless, such as connecting a car stereo or replacing lights. This is because instead of running miles of individual wires, you can connect them all to one point. 

Security and safety

Because the wires are connected tightly together within the end connection point terminal, the individual cables and components are less susceptible to the elements, vibration, and wear and tear.

Furthermore, much more space is optimized, and the risk of electrical shorts is significantly reduced. This is because the wires are taught and fixed within the terminal, therefore, are in a non-flexible position.

The wiring harness structure and how it connects sections together also reduce the risk of an electrical fire. 

What are the connectors for the car stereo wiring harness?

Technology has come a long way and thus so have motor vehicles and car audio systems.

The days that you have a power lead and wires connecting to your speaker are long gone. You now have many facets that a car stereo system can incorporate and use.

These features can include remotes, dimmers, illumination, and more, depending on the type of stereo you have. As I have already explained, all these wires are bundled together and conjugate at the harness terminal. 

Now, let’s look at all the primary connectors and wires you will find on a standardized wiring harness. This includes ones made by manufacturers and ones which you can purchase. This even goes for a harness that you can construct yourself because, as you will see, you’re able to buy specific connectors and cables.

The wire connectors

I briefly mentioned that in every stereo harness, you have two ends which are the male and female connectors, and this is a standard in the majority, if not in all cars. As an example, you can see Nilight waterproof connection terminals, which in addition will protect wires from a humidity if installed in wet conditions.

If you are replacing your OEM factory stereo, you will need to cut and use the original harness the stereo was delivered with ( I will explain how to make your own harness a little further). However, you could also purchase new connectors and create the new connection points all by yourself. 

The main takeaway from this is that the connection point will always have a male and female version where the one connects to the other and functions like a push-pull switch. 

RCA connectors

Because the speakers’ connection types are classified as low level, you can use an RCA connection terminal instead of a harness. 

Do take note, though, that if you plan to make your own harness, RCA connections can only be used on the wires associated with the speakers and only if your stereo or vehicle allows this type of connection.

The wires

By today’s standards, there are not only wiring harnesses that make connections much easier, but also color-coded wires are also helpful.

Before color code was introduced to the car audio, to make a harness and connect it correctly with the rest of the car audio equipment, you would need factory wiring diagrams. It can be challenging to connect wires that do not have corresponding colors not only in the car audio systems but also in other types of electric installations. 

Wire Colors for Car Stereo Installation

The yellow wire

The yellow wire is a direct line to the battery and is called the Constant Wire. This wire provides most of the power to your stereo and also a memory backup. When you turn your car on and off, your radio stations and all presets are saved. 

The blue wire

The blue wire is a remote turn-on or power antenna. This means, if you have another device (an amplifier with a remote connection point), the blue wire will be connected to that device, and every time your car stereo is turned on, the amplifier will turn on automatically.

In essence, it is a trigger wire turning on any device, and when a blue wire is missing or not connected correctly, you may see your battery drained. 

The green wires

Green wires are the leads for your left rear speakers. The solid green is the positive wire, while the green-black is the negative wire. 

The purple wires

Purple wires are the leads for your right rear speakers. The solid purple is the positive wire, while the purple-black is the negative wire. 

The grey wires

Grey wires are the leads for your right front speakers. The solid grey is the positive wire, while the grey-black is the negative wire.

The white wires

White wires are the leads for the left front speakers. The solid white is the positive wire, while the white-black is the negative wire. 

The black wire

The black wire is the ground wire, and this wire can be connected to either a metal section of the car or directly to the battery negative terminal. The black wire is effectively grounding the stereo to reduce any noise or interference.

The red wire

The red wire is the trigger wire that tells the car stereo to turn on when you insert and turn the key in your vehicle’s ignition system.

The orange wires

The orange wire will typically be an illumination wire. Some stereos have an orange-black wire, and this functions similarly to an illumination wire except that it is a dimmer wire.

From your dash, you can adjust the degree of illumination that is coming from your car stereo. 

What Is Car Stereo Wiring Diagram?

A car stereo wiring diagram is a graphical representation of which wires will connect to the terminal and their position.

Wiring diagrams often include a table or a list that will correlate to the wires and connection points. You can use a wiring diagram to understand what goes where effectively and, if need be, to route out any problems that may have occurred.

Furthermore, if you need to restore a wiring harness due to any reason, you will manufacture one to the correct specifications. 

 Take a look below at the example of a wiring diagram:

car stereo wiring harness diagram

What Gauge Wire Is Used for Car Stereo Harness?

Wire gauge, by its typical definition, is the measurement of a wire’s diameter. The size of the diameter will determine the amount of current that the wire can safely carry. The wire gauge will also determine the electrical resistance of the wire itself (its impedance).

Typically the car stereo will have wires with a wire gauge between 14awg and 18awg.

The power lead will have the thickest gauge (14awg), and the rest of the harness wire will be thinner, typically between 16awg and 18awg. 

How to Wire Car Stereo From Scratch?

Below I will explain how to construct your very own wiring harness, or in other words, how you should wire your car stereo from scratch.

You may need to make a harness for several reasons, including installing or upgrading your stereo or head unit or when your current harness and wiring are faulty in some way.

Tools to Build a Wiring Harness

How to Splice Car Audio Wires?

The first and most important factor we will have to grasp is understanding how to splice (cut and connect wires).

This is going to be the majority of the work in building a car stereo harness. Hence we have to understand the correct and incorrect ways to splice wires. 

The preferred method of removing the insulation shield is using wire strippers because they are specifically designed only to remove the wire’s insulation shield and not damage the internal wiring.

If you use scissors of any kind, you will most likely damage or remove some of the wire.

The best method of connecting wires together is to solder them. Many people often crimp wires together using a terminal, but that method is also subject to wear and tear and can eventually lead to faults.

By soldering the wires, you create a permanently fixed connection resistant to the elements and any form of wear and tear and vibrations of the car. To further protect soldered cables, it is worth using the heat shrink to cover the connection point. 

Heat Shrink is by far much more effective than electrical tape and is far more robust, withstanding a lot more punishment than electrical tape can handle.

Check out the video below, where you will see how to splice and connect car audio wire. 

How to Not Splice Car Wires Together?

When most individuals strip and connect wires, they will use a pair of kitchen scissors to strip the wire and then twist and bend the ends together.

Next, they will twist the two ends of the opposing wires together and then use electrical tape to cover the connection point. This way, although it somehow works, is the wrong way to cut and join wires.

Joining the wires together this way will increase the risk of losing them and creating a short in your stereo circuit. Furthermore, the electrical tape and connection are susceptible to the elements and vibrations of the car. This may eventually lead to wear and tear and even unraveling of the wire. 

Building a Car Stereo Harness

Now that you already know how to splice and join car audio wires together, we are ready to create our very own car wiring harness.

The first thing you need to do is determine why you need to make a new harness. You may do not want to build the harness from scratch but instead utilize the one you have on hand if possible. 

This means if you are replacing an OEM factory standard stereo, it will have a harness already connected to it that can connect to the harness in your vehicle. 

Logic would suggest that all you would need to do, instead of manufacturing one from scratch, is to cut the old stereo’s harness and implement it onto the new stereo. 

You could manufacture your own harness from scratch using the terminals as I suggested earlier and then run and solder each wire and connection point individually. This, however, would not be efficient.

The process would require you to cut out your vehicle’s harness and your new stereos harness. You would then purchase the individual terminals and connect each pair to the wire in your car and the corresponding wire on your new stereo. 

For the most part, you will have a harness that connects to your vehicle, so it will be best to construct your new harness from this one. 

All you need to do is cut the old harness at the appropriate length and then cut your new stereo’s harness to the proper size. If you find that one or the other is too short, you need to add some stereo wire between the two and compensate for length. 

The next thing you have to do is check any wire diagrams that your new stereo comes with and any manuals with wire diagrams that your vehicle is associated with.

With these two diagrams, you can determine which wires match and need to be soldered together to create the new harness.

After that, the only thing left to do is to splice the new stereo’s wires (harness) with your old stereos harness. The process is very straightforward and simple enough to manage.

If you prefer a visual aid, check this short video below. 


When a wiring harness is included, the whole wiring process is much more straightforward and can be done at a relatively low cost.

Although a harness looks complicated, it is just a terminal that connects many wires. Those wires are even color-coded (for car audio stereos) to lessen the risk of joining the wires incorrectly. 

It is much easier if you have a previous harness from your old car stereo because you know that harness is compatible with your car, and all you need to do is to splice your new harness to the old one.

Source list

A guide to car stereo wiring harnesses

How to install a car stereo

Cable harness