How To Correctly Install Your Car Stereo

I wanted to share a few tips on installing a new radio or CD player in your car correctly. I don’t know how many cars come into Metric Wrench Billings because someone has incorrectly installed their car stereo and we have to fix the wiring and all of the issues that arise because it was installed wrong. (BANG HEAD HERE)

When you purchase your new stereo, the very first thing that you should do is make sure that it’s going to fit correctly into the slot where your old one is. Make sure that if you purchase a wiring harness that it is the correct one for your car’s make and model as well as for the stereo that you purchased. Purchasing a wiring harness will eliminate a few headaches when you’re installing your new car stereo.

Make sure that you have all of the correct tools and material for installation! Some standard tools and material include: screwdrivers, write strippers, wire cutters and electrical tape.

Before you go any further, check your owner’s manual for specific instructions on how to remove the dash panel and how to CORRECTLY remove your old radio.


Removing Your Old Car Stereo

After you’ve reviewed your owner’s manual and you’re ready to go, the next thing to do is to disconnect the ground cable or the negative cable from your battery. DO NOT EVER work on the electrical system of any vehicle if this is connected!

Now you’re ready to remove the dash panel that covers your stereo! Unscrew and slide out the old head unit. At this point, you’re going to have one of two choices-a single plug with a ton of wires that connects to the back of your unit or a lot of individual wires. This next tip is KEY! If you see several single wires going into the back of your stereo unit, DO NOT detach them all at once. You’re not going to remember what goes where!

If you purchased a wiring harness, now is the time to plug the connector into your new wiring harness. This will then plug into the back of your new stereo and you can skip the next section, because you don’t need it. If you didn’t purchase a wiring harness, then keep reading!

Connecting the Wiring Manually

If you didn’t purchase a wiring harness, you are going to have to connect each wire yourself in order to install your new car stereo. So connect the positive wire from each speaker to the positive connector on the back of your new stereo. Next you would connect the negative wire. Note: If there is only one wire coming from your speakers, your speakers are grounded at the chassis, which basically means that you need to install new speaker wiring.

Next, you will connect the ground (-/black) wire of the stereo to a screw or bolt close to where the radio is mounted on the dash. The must be attached to metal! NOT fiberglass or plastic!

Whew! You’re almost done! (SMILE) Connect the 12 constant and ignition power wires (both +/red) to the new stereo. Go back and check your stereo’s installation manual to be sure that these get to the correct places.

Putting in the Car Stereo

Last process-you’re almost there! Take a look; you should have a single connector that connects all of the wiring in your car-either from the wiring harness or the one that came with your stereo that you have just finished connecting.

Now it’s time to ease your new stereo in the mounting bracket that came with it. If you didn’t measure correctly, you have to use the bracket from your old car stereo.

Plug the harness connector in the back of your new stereo; make sure that there is only one wire left from your old stereo now. This is the antenna which you can plug directly into your new unit. You may have a power antenna wire as well and you will need to connect that too!

Now it’s time to slide your new stereo into the slot in the dash, but don’t jump the gun here and screw it in, you need to test it out first! So go and reconnect the negative cable of your car to the battery. Turn your car on as well as your new stereo. Is there music coming out? Listen to ALL of your speakers to be sure that they are ALL working properly!

If everything is working properly, you can now tighten the screws so that your new car stereo stays in place and put the dash cover back on.


FYI: The number one reason that most newly installed stereos do not work is because of a bad ground wire. If you are experiencing this issue, look for another piece of metal to attach your ground wire too and try it again. Another suggestion is to get a piece of sandpaper and sand the surface of the metal before screwing the ground wire down to make a better connection.

For Volkswagen’s there is a wire that goes to the existing radio, if this wire goes to ground as it does in some of the aftermarket harness adaptors, it will cause no communication with the diagnostic scan tool. This is the most common problem that we see at Metric Wrench Billings.

And just a friendly reminder, don’t EVER work on the electrical system of your car when the ground wire is still attached to the battery! You can severely damage yourself as well as your car!