How To Wire A New Stereo In An Old Car (Step By Step)

Norvan Martin
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Upgrading the stereo in an old car can enhance your driving experience significantly. However, installing a new stereo in an old car may seem intimidating because of the seemingly vast differences between new and older stereo systems.

In most cases, you can install a new stereo in an old car with little to no trouble. All you need is some basic tools and our step-by-step guide. In this guide, we’ll walk through everything needed from gathering the tools to testing to ensure everything works properly.

Please however note that the process depends on both the make and model of the car as well as what type of stereo you desire to install.

Installing a new stereo in an older car may be daunting at first, especially if you are unfamiliar with car wiring. But with proper tools, knowledge, and patience – and with our step-by-step guide –  you can simplify the task.

Here is a step-by-step guide.

Step 1: Gather the Tools and Materials

Before starting the installation process, you need to gather all the necessary tools and materials. Here are some of the essential items you’ll need:

  • New stereo
  • Wiring harness adapter
  • Crimping tool
  • Wire stripper
  • Electrical tape
  • Screwdrivers
  • Pliers
  • Electrical tester

Step 2: Find a Power Source

Take a feed from a power source that is ignition-switched and run a wire of suitable amperage to your intended location.

Fit an inline fuse close to the power source on this wire; the size is determined by the maximum power requirements of the unit. Never use a fuse rated higher than the unit or its wiring.

Step 3: Power Back Up Wire

Take a wire from a permanent feed, such as a battery terminal, so your radio retains your preset stations.

Fit another inline fuse close to the take-off point.

Finally, run an earth cable from a suitable point on the chassis/body. This will be connected to the stereo’s black earth wire

Step 4: Disconnect the Battery

To prevent electrical damage during installation, first, disconnect your battery. Locate it and detach its negative cable.

Step 5: Remove the Old Stereo

Unscrew all screws holding onto it or use a pry tool to take out it before disconnecting any cables connected to it.

Step 6: Connect a Wiring Harness Adapter

Use a wiring harness adapter to connect the new stereo system with the car’s wiring system; use a crimping tool to secure wire connections.

Step 7: Connect Your New Stereo

To set up the stereo, connect a wiring harness adapter. Each adapter should include instructions as to which wires should connect where. Use a crimping tool to securely join them together.

Step 8: Test the Stereo

Before installing the stereo, test its operation thoroughly to make sure everything works as intended. Connect the negative cable from the battery back and turn on your car; check that everything appears normal before turning it back off again to see if your stereo works as promised.

Step 9: Secure Your Stereo

Once your new stereo has been tested and is operating as expected, secure it to the dash using its mounting screws. Make sure it remains securely fastened so as to provide an optimal audio experience in every drive.

Step 10: Secure Your Stereo

After installing your stereo system in your car, test its functionality again by turning on your engine and making sure everything works smoothly. Inspect your wiring to see whether everything looks tidy.

Step 11: Conceal Wiring for Safety and Convenience

Once everything is working perfectly, clean up the wiring using electrical tape to wrap and protect each wire and prevent shorts. 

Step 12: Reconnect Battery

Finally, reconnect the negative cable of the battery pack before restarting your car and testing out your stereo unit one final time.

Common Mistakes to Avoid

  • Not disconnecting the battery before starting the installation process.
  • Not using a wiring harness adapter.
  • Not testing the stereo before securing it in place.
  • Not tidying up the wiring after installation.


Wiring a stereo in an old car might seem daunting at first, but with the appropriate tools and knowledge, it can become simple. First research and purchase an appropriate wiring harness and mounting kit tailored specifically for your model car; next read both your stereo manual as well as car’s owner’s manual carefully, noting each wire’s purpose before making connections; lastly cut and strip wires carefully while testing before reassembling dashboard; by taking these steps you’ll enjoy both modern sound system while keeping the vintage charm of old vehicle alive!

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Norvan Martin is the founder of He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin