Car Stereo Installation: Wiring Harness Instructions for Stereos

Learn How To Remove a Car Stereo System and Install a New One

Replacing an old stereo is a great job for the do-it-yourselfer, whether you want to upgrade your existing system or make a repair. You can save a few dollars on installation fees that many shops charge. Stereo replacement is easier in some cars, especially larger cars like SUVs, because they have a little more working space behind the dash. If you haven't yet bought your components, take a look the "Find What Fits My Car" tool at  This will help you decide what type of car sound system will work best for you. 

These steps will teach you how to install a car stereo. It is important to note that although the installation instructions are easy to follow, please remember to pay special attention to your safety at all times.

  1. Before you begin, turn off the electricity to the car by removing the negative battery cable from its terminal. If your factory stereo has an anti-theft device, you'll want to get the code from the unit before disconnecting the battery.
  2. Next you need to know how to remove a car stereo system to get the old one out of your car. Remove the trim panels surrounding your stereo. Every car is a little bit different here. You will probably have to remove a few screws as well as a few clips in order to get the trip pieces off. These can be tricky to find as car manufacturers typically try to hide as many of these fasteners as possible. Some cars even have a few screws on the side of the glove box or behind cupholders.
  3. Remove the old head unit. This usually requires you to remove the screws holding the stereo to the inside of the dash. After removing the screws, pull the head unit straight out until you can reach the wires connected to the back. Disconnect the power cable, release the wiring harness and unscrew the antenna cable.

    The wiring harness is the plastic connector that incorporates all of the wiring for the speaker system into a single connection, or "harness." The factory stereo came with an adapter that mated with the factory-installed harness.

    Some cars, especially Ford vehicles, have two small holes on each side of the face of the Car stereohead unit. If your car has this setup, you will need to buy a simple car stereo removal tool from a car parts store in order to remove the radio from its slot.

    The car end of the wiring harness should have 4-8 color coded wires coming into the back of it. There are two wires that go to each speaker -- a positive and a negative. Most negatives are indicated with a black stripe. Positives wires are either solid colors or have a white stripe.

  4. Your new stereo probably doesn't come with an adapter that fits with the harness inside your dash. You'll need to buy a wiring harness kit from an electronics store. These usually cost about $10 or $15, and they're well worth the money. If you don't buy a wiring harness kit, then you will have to cut the wires to the factory harness. It will still work if you eliminate the harness, but you'll be doing yourself a disservice if you ever decide to change the stereo again at a later date.
  5. If you are installing a stereo that is smaller than its predecessor, you will need to purchase an adapter kit to properly adjust the fit of the unit. These usually cost about $12 and are available to adjust the opening for any of the car stereos.
  6. Install the new wiring harness. The new wiring harness will have to be connected to your new stereo. To do this, match each color coded wire to its mate and crimp them together. After you have connected all of the wires to their correct match, the stereo should be ready to install. You are now ready to test your car audio sound.
  7. Hold the stereo close enough to the dash to plug each of the connections into the back of the stereo. You may want to stop and test your work to ensure that you have correctly matched each of the wires on the harness. Test that the radio fader and balance adjustments behave properly.

    If everything seems to be in order, then you push the radio the rest of the way into the dash and mount it with screws.

  8. Once the stereo is properly mounted, replace the trim pieces and reattach the hardware holding them in place.


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