HomeTips & GuidesHow to Install an AUX Cable in the Car: Linking MP3 Player to Car Stereo

How to Install an AUX Cable in the Car: Linking MP3 Player to Car Stereo

Would you like to know how to install an aux cable in the car? Then you’re in the right place. 

An auxiliary input goes a long way toward improving the functionality of your car’s audio system despite the rise of competing technologies, such as Bluetooth. 

There’s just an unmatchable swagger in listening to music from your smartphone via the 3.5mm audio jack. 

We will bring you all the insights on adding an AUX input to your system in detail. Take a look. 

What Is the AUX Input on The Car Stereo?

An Auxiliary input (AUX Input) is a terminal that enables a connection to a signal source via a 3.5mm audio jack. It allows the connection of an audio source device (portable player), e.g., a smartphone or MP3 player, to the stereo system. 

Usually, we use a jack-to-jack cable to connect the external audio portable device to the car’s stereo system

How to Install Aux Input in Car Stereo

A jack-to-jack aux input cable.

A jack-to-jack aux input cable.

How you connect a device to the aux input will primarily depend on the two main conditions we’ll cover below. 

When the Head Unit has an Aux Jack

An Aux Jack in a Car Interior. 

An Aux Jack in a Car Interior. 

You can quickly connect any device if your stereo unit has a rounded 3.5 mm auxiliary jack. Most smartphones have an aux output, so most are compatible with this system. 

Therefore, confirm if the MP3 player or smartphone has an auxiliary jack. Next, look for a jack-to-jack cable with 3.5mm diameter plugs. Connect one end to the smartphone and the other to your car’s stereo system’s aux input. 

Usually, you’ll find the receiver connector on the front face of the stereo system. But at times, it could be on the rear side of the stereo system.

Therefore, to locate it, pull the stereo’s decorative panel, remove the stereo system and find the Aux Input (AUX IN). Now plug the jack into the terminal and restore the radio into place. 

So, does the stereo receiver take up all the MP3 or smartphone device roles? Well no. The stereo receiver is just a sound amplifier and volume controller. All the other functions, such as changing songs, are on the external device. 

When the Stereo Head Unit has no Aux Jack

An AUX Adapter. 

An AUX Adapter. 

Some radios lack the Aux Input jack, but that doesn’t mean you cannot connect an external device via the input. Here are the simple steps to follow: 

  • Check out your radio’s housing for the audio input connector. Usually, it’s on the backside if you cannot find it on the front end. 
  • You’ll need a cable with a rounded 3.5 mm diameter plug on one end while the other side features bare wires. You’ll also need a USB cable (assuming your radio features a USB connector but lacks an AUX input port). 
  • Now separate the wires of the 3.5mm diameter plug into left or right and connect them to the USB head. Cover the joints with electrical tape. 
  • You’ve now linked the USB cable to the 3.5mm diameter jack. Connect the jack head to your output device (smartphone or MP3 player) and the USB to the stereo receiver. You can now listen to music from your device on the radio speakers. 

The alternative is to install a Bluetooth Adapter to the car’s stereo system if your vehicle lacks the Aux port and Bluetooth functionality. You can pair your smartphone to the car stereo with the adapter. 

Can You Put An AUX Cord In A Cigarette Lighter?

If you like to go for the fancy, installing an AUX cord on a cigarette lighter is one option. But you’ll need an AUX adapter compatible with the cigarette lighter. Next, you can connect the cigarette lighter to the car’s stereo and play music saved on the external device. 

Best Audio Solution For Cars That Don’t Have An AUX Port

Prompt to connect a device to a car's Bluetooth. 

Prompt to connect a device to a car’s Bluetooth. 

If the car lacks an AUX port, can you still listen to music from your phone/MP3 player? Yes, you can. Most of the modern car stereo systems are equipped with Bluetooth. 

Simply find the Bluetooth feature on the stereo system, switch it on and connect your smartphone. Now you can listen to all your favorite content, such as audiobooks, podcasts and songs from the car’s stereo. 

Options To Connect Phone To Car Radio Without Bluetooth Or Aux?

What if you cannot use Bluetooth or AUX simply because your car has neither of the two features? If so, you can still connect your smartphone to the car stereo via the options we’ll explore below. 

Using an FM Transmitter

One solution is to connect via an FM Transmitter. Plug this device onto your smartphone/MP3 player jack. It will generate an FM signal that you can transmit onto the car’s FM radio. 

Next, choose an unassigned frequency on the car’s radio and set it to the frequency of the transmitting player. Now, you can play music from your device on the phone. 

Using a Cassette Adapter

Vintage 90's cassette tape placed on a car radio cassette

Vintage 90’s cassette tape placed on a car radio cassette

Like in the above case, you can use a cassette adapter to connect your smartphone to the car radio. Plug one end of the adapter (the one with the AUX jack) into the smartphone/MP3 player and the other into the cassette player. 

Now, play music and other audio signals from your smartphone on the car’s radio. 

Using a Wired Connection

The application of this option will depend on whether your car has a port designated for connecting to the car stereo system. Some of the cars feature auxiliaries such as a mini USB port. 

If absent, you can use any compatible adapter that plugs into your smartphone’s jack and the other end of the car’s stereo.

Alternatively, insert a Bluetooth adapter into your car’s sound input and connect your smartphone wirelessly to the car’s radio. 


Now, you have all the necessary insights on connecting an AUX input to your car’s stereo. 

Choose the integration method for the smartphone and car stereo system that best suits you.  There are a couple of affordable options we’ve covered in the guide. 

If you need these custom wires to update your car, contact us. We have advanced manufacturing processes and can get you at reasonable prices.

Hey, I am Lillian Yang, Sales manager of Cloom Tech.

I am a responsible, intelligent and experienced business professional with an extensive background in the electronics industry.

Reach me at [email protected] to get a quote for your projects.

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