This is my first Instructable, and describes how I connected my Ipod to my 2003 Prius. The information and options I found should help others add MP3 sound to any car. I'll present several solutions, along with pros and cons.
Step 1: Why Connect Directly?
When I first got my Ipod, I used a cheap cassette adapter to listen to podcasts in my car. The sound quality was so-so, and it occasionally malfunctioned. Eventually, the car's cassette player stopped working entirely, so I was motivated to look for a better solution.
First, figure out where you'll input the sound. If your (recent model) car has AUX or mp3 inputs built in, you're done, just use them. Otherwise, your options include tapping into a cable connecting one part of your sound system to another, or tapping into the head unit itself. The most popular option is to trick the car's audio system into accepting mp3 player input instead of input from the CD player - this is the option I'll describe in detail. Search your car's audio model number on the internet for information about your system, and figure out where (ie which pins or wires) the input goes.Is sound quality and volume important? Just sound, or should the car charge your Ipod, too? Do you want a system that works with any MP3 input, or just your Ipod? Do you mind adding switches on the dashboard? Do you mind a cord sticking out of your dashboard? Do you want to continue using all the sound options on the car, or will you sacrifice one of them? Do you want to do this cheaply, or will you spend more to get a slicker solution?
Which kind of input? The mini stereo connector on the Ipod (where you plug in the earphones) is in the R/L/Ground form. An older or simpler car audio system may accept input in the R/L/Ground form, but newer systems more likely use R+/R-/L+/L-.
(Briefly, the R+ and R- are inverse to each other - the car audio system uses the difference between the two signals. This yields more volume and less distortion than comparing R to ground.)
The CD cable in my car includes wires R+, L+, R-, L-, signal ground and electrical ground. Since the Ipod only has R, L and ground, the question is how to connect them for the best sound quality and volume. Connecting the Ipod ground to the audio system's R- and L- cables sounds good when the Ipod's playing, but you sacrifice quality and volume of sound from the CD player if you leave R- and L- connected together.
So - if you're choosing a "piggyback" approach (leaving the connection in place all the time), connect the Ipod ground to the cable's signal ground. If you're using a switched approach, connect the Ipod's ground to R- and L-. (Don't connect the Ipod audio ground to the car's electrical ground - depending on the car audio system this could fry your speakers or your Ipod.)
Step 2: Option 1: Audio Jack and Silent CD
Option 1: Audio jack and silent CD
You can play a CD of silence on the CD player while piggybacking input from the MP3 player.
The only parts you need are a little wire and an appropriate jack and cord:
RadioShack 1/8" Stereo Panel-Mount Audio Jack (2-Pack) Model: 274-249 | Catalog #: 274-249
RadioShack® 3-Ft. 1/8" Stereo Plug Cable M/M (White) Model: 4200759 | Catalog #: 42-759
Make the following connections from the audio jack to the CD player cable:
Ipod L (Tip of the plug) to CD player cable L+
Ipod R (Ring of the plug) to CD player cable R+
Ipod ground (Sleeve of the plug) to CD player cable signal ground
The following Instructable presents this approach, and also has instructions for making a silent CD:
Pros and cons:
This method is fast and cheap.
Works for any MP3 device.
You have to use a silent CD.
Because you are taking the Ipod's output in the R/L/ground form and only giving the car only R+/L+/ground instead of R+/R-/L+/L-, the volume of sound is less than normal, and the quality of the sound might not be quite as good. The volume changes according to the Ipod's volume - what this means practically for me is that I have the Ipod's volume cranked up all the way, and still have to turn the car audio system's volume up. So when I switch to using the Ipod with earbuds, the volume's up too high, and when I listen to the car radio, it's too loud as well.
Step 3: Option 2: Audio Jack and DPDT Switch
Option 2: Use a closed circuit audio jack and a double-pole-double-throw (DPDT) switch to disconnect the signal from the CD player when your Ipod is plugged in.
A closed circuit jack makes one set of connections when not in use, then different connections when a plug is plugged into it. This is how your radio turns off the speaker when the earphones are plugged in, or switches from battery to corded power:
Radio Shack 1/8" Stereo Panel-Mount Phone Jack Model: 274-246 | Catalog #: 274-246
If you found a R/L/Ground place to tap into your sound system, this is perfect: just connect the jack in a way that it switches from the car's signal to the Ipod's.
If your car has R+/R-/L+/L- input, it's not so simple. You can connect the output from your Ipod to R+/L+ and ground, but the car's CD player is still putting out a signal on R-/L-, so you'll hear your Ipod's output in addition to the CD player's, each at half volume. Replacing the R+/L+ signal alone isn't enough. (That's why option 1 uses the silent CD).
You can still use this approach with a R+/R-/L+/L- system and a non-silent CD, but you'll need to use a single closed circuit audio jack and a DPDT switch, such as:
DPDT Submini Toggle Switch Model: 275-614 | Catalog #: 275-614
With the closed circuit jack, make these connections:
Not plugged in:
CD R+ output to car's R+ input
CD L+ output to car's L+ input.
Ipod R output to car's R+ input
Ipod L output to car's L+ input
Ipod Ground to switch (Below)
With the DPDT switch, connect:
CD R - output to car's R - input
CD L - output to car's L - input
Ipod's Ground to car's R - input.
Ipod's Ground to car's L - input.
Pros & Cons:
Sound is quite good.
Does not need a silent CD.
Have to flip a switch to silence the CD player.
Can use this with any MP3 player, not just an Ipod.
Step 4: Option 2 in Action
Here's what it looks like. I drilled two holes in a free area of the plastic dashboard cover, each 1/4 inch in size.
In use, I flip the switch up and unplug the Ipod cable to listen to the car's CD player. I plug in the cable and flip the switch down to listen to my Ipod.
On the dashboard controls of the car, I have to select CD Player and have a CD playing. This "tricks" the car's audio system into accepting the input from the Ipod.
Step 5: Option 3: Docking Adapter (My Favorite!)
Option 3: Use an docking adapter cable to get input from the Ipod connector.
Two dashboard switches change from CD player to Ipod. (Addendum - since I wrote this, I found miniature 4-pole double throw switches, so you can do this with one switch instead of two. I did this successfully on another car.)
With this option, you can charge the Ipod in the car, and the sound is "pre-amp level", since it's coming from the Ipod connector rather than the audio jack. The volume control on the Ipod is no longer used.
You do not need a silent CD, and can alternate between Ipod music and CD music by flipping two switches.
This won't work with other MP3 players, since the adapter cable is unique to the IPod.
Step 6: Adapter Cable
Adapter cables like this are available from Radio Shack:
Radio Shack Gigaware™ Composite A/V Cable for iPod® and iPhone® Model: 12-579 | Catalog #: 12-579
However, I opted to buy a cable online in order to be able to charge my Ipod as well. I bought an Axxess AIP-RCA5V. This will charge newer Ipods.
The older Ipods which used firewire charging may not charge with this cable.
Addendum: I've since upgraded to an Iphone 5, and was able to use this same setup with an adapter cable from Apple. I would not recommend getting third-party adapters: the new Iphone uses digital sound, and the $$ Apple cable includes analog-to-digital conversion.
Step 7: Loosen the Dashboard Cover
First, get at the wires. I removed the lower part of the dashboard to reveal the CD player, disconnected it from the sound system and brought it and the dashboard cover into my shop to work on.
You can probably find instructions for getting at your player on the internet, or ask the kid who does the installations at your local car audio place.
On my 2003 Prius, I removed the plastic cover of the lower dashboard by removing the black plastic buttons on either side.
Press down the middle of each button with a nail or punch, then remove them. You'll be able to wiggle the dashboard cover forward.
Step 8: Free the Dashboard Cover
Once the cover is loose, remove the connectors to the power socket / cigarette lighter and pull away the tiny lightbulb that illuminates the change drawer / ashtray.
Step 9: Detach the CD Player
Next, remove the four screws that hold the CD player to the dashboard and pull it forward.
Step 10: Disconnect the Grounding Screw
Unscrew the grounding wire that connects the CD player to the frame of the car.
Step 11: Disconnect the CD Cable.
There's a tab on the connector between the CD player cable and the cable to the car's audio system. Press it down and pull them apart.
Step 12: Time to Solder!
I found this information about the wires on my car's audio system online:
"R4 Color" refers to the cable in the car, so I added the colors for the CD cable, and made a mirror copy of the pin number chart from the perspective of the CD cable, since that was the side of the connecter I was working with.
Step 13: Construct the Cable
Get some colored cables and and use them to connect the CD cable to the two DPDT switches. (or to a single quad-pole double-throw switch.)
For each of the four channels in the CD cable (R+, L+, R-, L-), I cut the wire near the connector, soldered a wire to each cut end and brought the pair of wires to the switch: one in from the CD cable, one out to the car audio system. Be careful not to bundle the wires to and from the CD together, or you may notice an antenna phenomenon: when the switch is in the Ipod position, but the Ipod is not connected, you hear the CD faintly.
Additional wires to the switches connect to RCA connectors which receive input from the Ipod adapter cable. (You could also circumvent the RCA connections; I chose to use them in case I later have to switch to some other kind of adapter cable, ie for some other kind of MP3 device.)
Step 14: Connecting the DPDT Switches
Make sure to mark the top of each switch, and wire them carefully so that flipping the switches up selects the CD player, flipping them down selects the Ipod input.
Each DPDT switch has three rows of two connectors.
When the switch is up, the connectors in the middle are connected with the connectors on the bottom.
When the switch is down, the connectors in the middle are connected with the connectors on the top.
On the first DPDT Switch:
Solder the R+ and L+ wires out to the car audio system to the middle connectors.
Solder the R+ and L+ wires in from the CD cable to the bottom connectors.
Solder the R and L wires in from the Ipod cable to the top connectors.
On the second DPDT Switch:
Solder the R- and L- wires out to the car audio system to the middle connectors.
Solder the R- and L- wires in from the CD cable to the bottom connectors.
Solder the ground wire in from the Ipod cable to BOTH of the top connectors.
The photo shows the second DPDT switch. Each connection is soldered, then covered with heat shrink tubing.
Step 15: The Finished Cable
This shows the end of the finished cable, including the two DPDT switches and the RCA connectors.
The other end connects to the CD player cable.
Addendum - when I repeated this process for another car, I used a 4PDT switch. I also used placed a connector in the cable going back towards the CD player, to allow me to replace the switch if needed without disassembling the dashboard or soldering in my car!)
DPDT Submini Toggle Switch Model: 275-614 | Catalog #: 275-614
Gold-Plated Panel-Mount Phono Jack Model: 274-852 | Catalog #: 274-852
Step 16: Connecting the Power
I had these battery connectors lying around, so I used them to connect the 12V power and (electrical) ground wires for the adapter cable (so it can charge the Ipod). I connected one set to the power and ground wires on the adapter cable, the other one to power and gound from the car itself.
Note - since these two connect to each other, the red and black cables are different on each side of the connection!
Heavy-Duty 9V Snap Connectors Model: 270-324 | Catalog #: 270-324
Step 17: Power Connection at the Dashboard
I soldered the other connector to the back of the power outlet / cigarette lighter.
At this point the red wire is 12V, connected to the center pin of the power outlet / cigarette lighter.
The black wire is ground, connected to the rim of the power outlet / cigarette lighter.
Just to add to the confusion: On the power outlet, the spade connector marked "12V" is actually the ground!
Step 18: Fishing the Cable
I wanted the Ipod adaper cable to come out of the console between the front seats, so I removed the console and used a stiff piece of metal banding (from a packing crate) to fish the cable under the carpet.
Step 19: Cable Ready
This picture shows one end of the Ipod adapter cable coming out of the dashboard, the other end coming out of the center console.
Step 20: Ready to Install
The CD player with its cable (and the newly constructed cable with the DPDT switches) sits in front of the dashboard.
(addendum - as noted above, don't bundle the wires to and from the CD player together!)
Step 21: Dashboard Spaghetti
Cables are labeled in the drawing.
The next step is to connect the ground wire to the CD player and connect the CD cable to the car audio system cable, guide all the cables back into the dashboard and screw the CD player to its bracket.
Step 22: Connections to the Dashboard
Here you can seen the two DPDT switches installed in the dashboard cover (make sure they are right side up!).
(Each hole is 1/4 inch in diameter; check and make sure there's enough room around the hole for the switch itself.)
The power connector has been snapped together. I covered this with electrical tape after the photo.
The RCA connectors are joined - I covered them with electrical tape after the photo.
The change drawer light and the power connector from the car to the power outlet / cigarette lighter have not been connected yet.
Step 23: Finished!
Here's the final product: My Ipod sounds great in the car and charging it on my commute means it never runs down. The cable tucks out of the way in the console. Two discreet little switches on the dashboard switch from the CD player to the Ipod.
I hope you've enjoyed this instructable (my first!), and are inspired to add MP3 sound to your own car.
Option 4: While I was thinking about this project, I found a cool idea - using relays to switch between the CD player and Ipod, instead of two DPDT switches:
Relays and relay sockets can be found at
This method is really slick, but installing two switches in the dash just seemed easier to me. (....or just using a single 4PDT switch!)
Option 5. Commercial adapters. If you drive a late-model car, there may be a readymade Ipod adapter for your car that might even allow use of the dashboard controls and/or touchscreen to control the Ipod.
Step 24: Addendum: What I've Learned Since I Wrote This.
Since I wrote the above instructable, I've added Ipod sound to a second car, and learned a few things:
1) Don't bundle the wires to and from the CD player together. If you do, you can get an antenna effect: when the switch is in the Ipod position but the Ipod is not connected, you hear the CD faintly.
2) I used a 2-pin inline connector to the cigarette lighter instead of the goofy 9V battery connector.
3) I used a 4PDT on/on toggle switch instead of two DPDT on/on switches. I'm not listing the supplier here, because the ones I bought turned out to be pretty flimsy. I reinforced them with epoxy after the first one I used fell apart.
4) I used a 9-connector connector on the wires that run back to the CD player - that way, if I have to replace the switch, I don't have to dismantle as much or do a lot of soldering in the car.
5) I've upgraded to an Iphone 5, and was happy to find it works fine, just by adding Apple's adapter cable. Even though the Apple product is expensive, be cautious about third party 30-pin to Lightning adapters, since the Iphone 5 uses digital sound, and the Apple adapter included an analog-to-digital conversion chip. Also, other adapters may or may not be able to charge through the Lightning connector.