How To Wire a Car Stereo From Scratch?




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Have you ever traveled in an excellent car but had low-quality music? Unfortunately, this has been an issue in most cars.

Generally, many cars come with factory-fitted head units that are not up to the mark. This is because most car manufacturers do not put the highest effort into a car’s sound and audio equipment quality. 

The most common and best decision is then to replace the car head unit with an aftermarket radio, but how to wire a car stereo from scratch? Let’s find out.

The first step into wiring a car radio is to remove the wiring harness and disconnect wires connecting the speakers and power. Next is to attach the wires to the new harness or the harness adaptor and plug it into the new radio. When connected, test the car radio and if it works correctly, place it in the dashboard.

Tip:  While doing any work related to the car electrical system, you may need a good multimeter.

This simple tool allows you to make quick tests of the wires and their connections.

The entire replacement process involves the installation and wiring of the car radio. In this article, I will show you a step-by-step guide on how to wire a car radio.

How to Wire Car Radio From Scratch. A Comprehensive Guide.

Like other processes, following the proper instructions of wiring the stereo ensures you have high-quality audio in your car.

Take time to read every step carefully and act accordingly. Ensure you do not work in a hurry and pay much attention to the job.

What Tools Are Needed to Wire a Car Stereo?

Before doing anything to the car radio, there are some basic but necessary tools you should have prepared.

AstroAI Digital Multimeter, Voltmeter 1.5v/9v/12v Battery Voltage Tester Auto-Ranging/Ohmmeter/DMM with Non-Contact Voltage Function, Accurately Measures Voltage Current Amp Resistance Capacitance

You probably have all in your garage, but if not, I added the Amazon links to tools I use, and I am happy with the quality:

  • Digital multimeter.
  • Wire strippers.
  • Crimpers.
  • 9-volt battery or speaker tester.
  • Electrical tape.

Step 1: Remove the Radio and Disconnect the Wiring Harness

First, remove the old stereo from the dash and disconnect the wiring harness. At this point, depending on the new radio, you may need a wiring adapter to help you connect your new car radio to the existing clip of the car.

RED WOLF Replacement for 2007-2011 Dodge/Chrysler/Jeep Car Stereo Wire Harness Aftermarket Radio Sirius CD Player Install Connector Adapter

A wiring adapter helps connect unique car stereos with the standard DIN connection from the car and avoids any misconnections. 

Step 2: Disconnect Battery

When doing the wiring process, you will have to work on the electrical system.

Hence, there are chances of electric shock, and this is why it is recommended to disconnect the battery before starting the wire connection process.

In most cars, you will find the battery under the hood, with some rare cases when installed in the back of the vehicle.

After locating the battery, use a hand or socket wrench to loosen the black cable from the negative terminal of your battery. 

Consider losing the bolt and pull the cable down to the battery side to ensure it does not touch the positive wires. Failure to disconnect the battery may harm you or the car’s electrical equipment.

Step 3: Wrap All Connected Wires

The significance of doing this is to secure their connection points.

After checking all the wires and connecting them with the car, it is essential to make the connections permanent.

Ensure there is no bare wire in the car radio, and to warp the wire connections, you can use electrical tape.

You can use other ways to wrap wires, but using tape is the easiest, cheapest, and most common method many people use.

Wire Harness Automotive Cloth Tape - Adhesive Strong Abrasion Resistance Heat Proof Electrical Flannel Tape for Wrapping Wiring Harness/Insulation/Car Engine (3/4" x 50 ' Pack of 1 Piece)

Step 3: Test Your Car Radio

After making the connections and securing them, you have to reconnect the battery to be able to test the stereo before placing it permanently in the dashboard.

It is advisable to install the car radio after checking it is working perfectly. First, however, you need to check its all functions, including speakers connections.

Finding something that is working incorrectly means the wires are not connected right, and often mistake is wrong connection of the speaker wires. 

Step 4: Place the Wires Harness Into the Dashboard

After ensuring that all of your connections are tight and secure, it’s now time to install wiring inside the dash.

This includes connecting an often-forgotten antenna wire from car radio signal reception equipment so you can enjoy clear communications while driving!

You have to remember that there should be enough space for your radio in the dashboard, so make sure all wires are pushed into the dashboard.

This way, the stereo won’t get stuck when trying to move or remove from its position later on without damaging anything!

Step 5: Place the Car Radio Into Its Place

In most cars, there is an opening inside the dash where the car radio should be placed.

While installing the car radio, make sure it perfectly fits into the slot, and there are no extra wires that would block free movement.

If you feel some resistance while pushing the radio, never force it with too much pressure to its position. Otherwise, you can damage the wiring connectors at the backside. 

In this case, an adaptor is very helpful at sliding the car radio properly in its correct position. An adaptor is available at any electronic store or auto parts store.

Step 6: Secure the Car Radio in Its Position

You can secure a car radio into two main methods.

  • One of them is for the car radios that need spring clips. Once the stereo is locked at the correct position, the clips close and you can hear a click sound.
  • The other one that is less common, involves brackets and bolts that need proper fixation. Bolting the radio permanently helps to secure it in the place.

Step 7: Install Dashboard

This is the final step of the wiring process and involves assembling every piece of the trim and the plastic clips.

At the same time, be careful to avoid the damage of any plastic parts and take time to check if the overlapped pieces have been correctly layered.

If you come across some plastic parts that have been broken, you can use hot glue to secure them.

However, using glue is not highly recommended since the plastic parts you fix can become difficult to remove in the future. 

If the entire rim piece has been broken completely, the only option you have is to buy a replacement.

How to Test Car Radio Wire for Their Right Connections

All wires have to be in good condition and connected to the radio without interruptions.

Below I listed a few simple checks you can do to make sure the stereo’s connection is correct:

Constant wire

This wire comes with 12 volts, and it supplies power directly from the battery.

To test if it is working, the first thing you should do is put off your ignition. Afterward, ground the black wire, pick up the red meter probe and connector, and touch it with the constant yellow wire.

The constant wire should give the reading up to 12 volts with a 0.5V difference.

Speaker wire

The simplest way to test the speaker wires is to use a 9-volt battery. You can also use a multimeter to test the speakers but make sure you set it to resistance before testing.

Accessory Power

Turning off the ignition makes the wire show a zero volt reading at a meter. Upon turning it on, it reads 12 volts and 0.5 volts.

Ground wire

Identifying the ground wire is straightforward after identifying the constant wire. Then, after proper testing, the ground wire is connected to the black wire.

Note that it is necessary to begin attaching a red meter probe with constant wire and later a black meter probe with the wire you are testing.

If the reading on the meter is similar to the constant wire testing, that is the ground wire.

Frequently Asked Questions (FAQs)

Where Is the Ignition Wire Located?

Depending on the car, the ignition switch harness is located inside the steering wheel column on either the left or right side.

The ACC wire is the one often 18 gauge yellow or pink. Installing this wire at a local electrical specialist can help you ensure the installation.

What Happens if You Do Not Ground a Car Stereo?

It is impossible to operate a car stereo without a proper ground wire installed.

The correct ground connection allows your radio to work perfectly without malfunctioning issues when the car is on.

How Can I Tap the Wires When Wiring a Car Stereo Without the Harness Clip?

The best solution is to look at your car’s electrical manual. However, if the manual is unavailable, you have to trace every wire.

Using a multimeter will be a good idea in this task. Since car electrical systems can be tricky to manage, do not attempt to play with the car’s electrical system without basic knowledge.


You have no reason to stay in an excellent car with a poor music system with the above guides.

Remember, adding a new car radio in your car is a great way to breathe new life into your vehicle. However, for the stereo to work at its own best, you have to follow the installation and wiring process.