There is lots to love about cars from the 1980’s and 90’s. One thing that is hard to love is the audio technology manufacturers used during the time period. As the battle for market supremacy raged between cassette tapes and CDs, companies tried to meet consumer demands with some truly funky head units. Today, both tapes and CDs have gone the way of the dodo, and new options for music offer far better audio quality and portability.

Collector and enthusiast preferences have changed in recent years. These days, cars from the 1980’s and 90’s are starting to increase in value, and buyers who were too young or too poor to buy what they wanted when these cars were showroom new are finding good condition cars at reasonable prices.

Adding Modern Functionality to Any Car

Have you seen the value of a 1993 Ford Mustang Cobra recently? How about a 1991 Acura Integra Type R? Original, high quality cars have shot up in value in recent years as interest by enthusiasts and collectors has grown.

Cars from this era are a blast to drive, but cutting up the dash to install an aftermarket stereo that offers modern playability is going to tank the resale value. A collector is not going to want to buy a car that has been cut up and modified, no matter how cool the stereo installed in the car is. So, if you are not going to add a modern head unit, how can you play MP3’s or stream music from your smartphone?

Adding an Aux-in port will let you play music from an MP3 player, your smartphone, or whatever digital device you like to use that connects with a 3.5mm headphone-type jack.

Installing an aux-in port is a simple job the average do-it-yourself home mechanic can accomplish with professional looking results in an afternoon. There are many different ways to add aux-in functionality to any car, truck, boat, or whatever else you drive. Even motorcycles can be set up with aux-in playability.

Options Abound

First things first, identify the options you will have for your particular stereo. If your stereo has RCA input ports on the back, you can simply purchase an adapter cable that will plug into the RCA port and your music playing device through a 3.5mm male cable.

Many cars came with ports for CD changers. Adapters are available for many popular models that allow you to simply plug into the CD changer port and add an Aux-in terminal. It is worth taking a minute to search the internet for your particular year, make, and model of car to learn about possible options. Many popular brands have adapters available to work specifically with factory-installed radios. These can be more expensive than doing it yourself, but offer convenience and a clean installation.

Things to Look For on Your Head Unit

If your car or truck has an Aux-in port but it is in a dumb location, or if you just want to add one in a different part of the car, it’s a very simple operation. Remove the port from the dash, or wherever it is located, then cut and splice an Aux-in cord into place, safely routing it to where you want to add a port, and install the new port in a smart place.

Waterproof aux-in housings can be used to install a port on a boat or on the outside of a vehicle, like in the bed of a truck so you can blast your tunes at the next tailgate party before the big game without opening the doors.

If your stereo does not have RCA ports or CD changer controls, you can wire them into the existing stereo. This will require a little bit of knowledge and skill. You will have to remove the radio from your car and disassemble it to make the necessary changes.

Aux-In Port for Mobile Tunes

Auxiliary input ports, called aux-in for short, first appeared in the 1980’s to allow consumers to play tapes and CD’s from a walkman or discman-type player through the car stereo. Once head units started having CD players, many factory head units stopped including the aux-in port. MP3 players had yet to hit the scene, so there was simply no need for the redundant port.

Aux-in ports deliver near CD-quality sound, unlike the cassette or disc adapters that are notoriously bad sounding and do not last long. A device called an FM Modulator can be used to play music from an MP3 player, but modulators have a bad reputation for poor quality sound and can be expensive. They also will not work well without a strong FM signal.

Getting To Work


You should know how to solder and use a Multimeter.


Get the best quality repair manual for your car that you can find.

These items can usually be purchased at electronics supply stores in your home town or online from vendors such as

A method of mounting the jack, like drilling a hole somewhere inconspicuous. Many ports are surface-mountable.

AM and AM/FM Radios

The original head units that featured AM and AM/FM are becoming more rare and valuable to collectors, so don’t throw them out. It is easy to add an aux-in port to these stereos.

Get the best quality service and repair manual available for your car. Try to find the workshop manual issued for professional mechanics, as these manuals provide the best, most accurate information.

Before working on any part of any vehicles electrical system, disconnect the negative battery terminal. Safety first. No one wants to get electrocuted and setting your car on fire probably isn’t what you are trying to do. And it’s no fun finding a fuse that you blew when you short something out on accident.

Disassemble Your Dash

You will need to remove the stereo from the car and open the case, exposing the innards of the head unit. Use a high quality service manual for your vehicle that provides instructions on how to remove the radio correctly.

You will find wires running from the tuning knobs or buttons to a cylindrical part mounted to the computer board. This component is called a potentiometer, or pot for short. It is a rotary switch that allows multiple functions in a compact space.

You will need to identify which wires run to the volume control portion of the pot. A wiring schematic is helpful if you have one. Otherwise, with the radio sitting upright, the wire on the bottom terminal is typically the input, the middle terminal is the output, and the top one is the ground terminal.

Prepare the Head Unit for Modern Convenience

You can unsolder the input wire from the pot at this point. Most head units will have a light blue input wire. This wire will be connected to the Aux-in jack and a new lead wire will be run to the pot.

Using the multimeter or a manufacturer schematic, identify the function of the pins on the Aux-in port.

Identify where you want to install the jack. Typically, near the radio is preferred, but I like to put mine in the glovebox or in an ashtray. I think it keeps it clean and doesn’t take away from the factory appearance.

Make Good Connections

Now, it is just a matter of hooking the wires up correctly. Easy. Get your soldering gun ready!

Solder a jumper wire from the input on the pot to the terminal that gets power when a 3.5mm plug is connected to the circuit.

Solder a jumper wire from the ground terminal on the pot to the ground terminal on the Aux-in port. You do not need to remove the existing ground wire.

Solder a jumper wire from the old input wire to the remaining terminal on the Aux-in port.


Now, all that is left is to reassemble your radio, route the wires safely, install the jack, and reconnect the battery.

With the car on, plugging a 3.5mm cable from an MP3 player or smartphone into the port will allow playback through the factory speakers and volume control will function like original. If the head unit plays music in mono, you will need to plug a mono-to-stereo adapter in to get good quality playback.

When the plug is removed, the radio will play normally.

The process may sound intimidating, but the results are very rewarding. If you take your time and follow the steps correctly, installing an Aux-in port in your car is a straight-forward project you can complete yourself.