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HomeTips & GuidesHow to Wire a Stereo Into a Car Without a Harness

How to Wire a Stereo Into a Car Without a Harness

How to wire a stereo into a car without a harness? If you want to install a new stereo and your car already has a factory harness, you can do it in two ways. 

You can get a compatible adapter to plug into the existing harness or fabricate a new one

Otherwise, you can cut and connect the harness wires directly to the new harness, which, however, will lead to another set of problems if you want to upgrade the stereo in the future.

However, it’s common to wire a stereo without a harness. Surprised? Yes, it’s true.

Let’s find out “how to wire a stereo into a car without a harness” in this blog post.

Table of Contents

Wiring a car stereo without a harness

Wiring a car stereo without a harness can have multiple meanings: Wiring without a factory harness, Wiring without a head unit harness, or Wiring without any harness. We will discuss all of them here.

Wiring a car radio without a factory harness:

Suppose you have everything, including the pigtail, that comes with the head unit, but someone has cut the factory harness out of your vehicle. Now, when you remove the head unit, you will have bare wires.

  • In such a situation, first, find out the wiring diagram corresponding to the make and model of your car. You can search online or look into the manual that comes with a vehicle. 
  • After you find the diagram, you can locate the different wires, their functions (power, ground, memory, speaker, etc.), and their corresponding colors. 
  • Once you have this information, you can cut the aftermarket harness and rebuild everything from scratch.
  • Connect the head unit harness directly to the factory wires in the dashboard according to the wire colors and their functions.

Suppose you did not get the wiring diagram and want to do things from the start. 

Firstly, determine each wire’s function using a multimeter, test light, or battery, which will take a few minutes. 

Once you do this, you can opt for any way mentioned above to connect the head unit.

Behind the head unit

Behind the head unit

Wiring a car radio without a head unit harness:

If you have a factory stereo harness but do not have a head unit harness, you can either purchase an adapter or fabricate a new one.

Find a replacement harness:

You can either get a new or a used harness for this purpose. Getting a used one from a nearby wrecking yard would be much better.

Fabricate a new head unit harness:

Get the pinout diagram of your car’s head unit. Enter the unit’s model number in Google, and you will get one online. 

You may also check the vehicle’s manual for the same. The pinout data will help you to make a new head unit harness. For this, get a connector suitable for your car’s head unit.

Often, you need a two-row header connector (rectangular) with a through-hole mount female socket. 

Basically, the connector is designed for installation on the circuit board, but you can also use it as a base for a replacement stereo harness.

Sometimes, finding a connector with the correct pin number and spacing is difficult. If that’s the case, do not focus on the pin numbers. 

Only look for a connector with the correct pin spacing. You can also use many small connectors or cut a large connector to fit the head unit size.

Once you have the connector, solder all the wires to the connector pins and finally secure them with the heat shrink to avoid short circuits.

Custom pigtail wiring harness for your head unit

Custom pigtail wiring harness for your head unit

Wiring a car stereo without any harness at all:

In this case, your head unit has no harness, and you deal with bare wires in the car. In such a situation, you can find a solution by combining the above two methods.

  • First, get a pinout diagram for the head unit and build a new harness. 
  • Once you have a newly designed head unit harness, determine the functions of each wire in the dashboard, such as power, speakers, ground, and memory.
  • After you know all the wires’ functions, create a new harness of these factory wires or connect them directly to the head unit harness.
Custom car Stereo Wire Harness 

Custom car Stereo Wire Harness 


Vehicle wiring harnesses are essential; you may need to create one in different situations. 

For example, you can install a new device, upgrade an existing one, or replace a faulty harness. 

If you know the correct method and understand the vehicle wiring properly, things become easier for you. 

Contact Cloom for any help regarding custom wiring harnesses. We manufacture custom-designed wiring harnesses and cable assemblies used in various applications.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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