Reverse Engineering Enables Slick Bluetooth Solution for Old Car Stereo

Those of us who prefer to drive older cars often have to make sacrifices in the entertainment system department to realize the benefits of not having a car payment. The latest cars have all the bells and whistles, while the cars of us tightwads predate the iPod revolution and many lack even an auxiliary input jack. Tightwads who are also hackers often remedy this with conversion projects, like this very slick Bluetooth conversion on a Jeep radio.

There are plenty of ways to go about piping your favorite tunes from a phone to an old car stereo, but few are as nicely integrated as [Parker Dillmann]’s project. An aftermarket radio of newer vintage than the OEM stereo in his 1999 Jeep would be one way to go, but there’s no sport in that, and besides, fancy stereos are easy pickings from soft-top vehicles. [Parker] was so determined to hack the original stereo that he bought a duplicate unit off eBay so he could reverse engineer it on the bench. What’s really impressive is the way [Parker] integrates the Bluetooth without any change to OEM functionality, which required a custom PCB to host an audio level shifter and input switch. He documents his efforts very thoroughly in the video after the break, but fair warning of a Rickroll near the end.

So many of these hacks highjack the tape deck or CD input, but thanks to his sleuthing and building skills, [Parker] has added functionality without sacrificing anything.

18 thoughts on “Reverse Engineering Enables Slick Bluetooth Solution for Old Car Stereo

  1. Kind of gutted to learn that cars from 1999 qualify as “old” and that old radios even lack an input jack.
    our car radio has a tape slot and LW/MW radio, and obviously a speaker, yes just the one.

  2. My new truck (replacing a 16 year old, 200K miler with original clutch) has inputs. Previous had a CD player until about 2010 (it ate a disk and died), and, prior to that, cassette and 8-track. With the input available, I can put the 8-track back in. Glad I saved it.

  3. The tuner (RF front end included) on a chip that is in stuff nowadays is total crap. Yes older tuners pre-2000 are about as good as it gets. That wonder on a chip is just miniature mediocrity not performance. Blurtooth is just about the same, and can’t get any better with out going to wifi bandwidth. Agree on leaving original factory radio and upgrading everything behind it’s panel but keep a hard wire connection to media even if it’s mp3 stuff. When you can take a non appul phone and whip out high def tunes to that stereo you don’t want rusty steel rims instead of alloy rims on your whip.

    If the radio has a dual pot for volume, intercept the incoming third terminal. If the volume is touch (till things get totally digital) there is a volume-eq chip that has a pair or more of inputs. The one pair form the CD or tape are the ones to intercept and input your external source.

    Please drive safely and don’t look at and interact with a screen whilst driving.

  4. I want a MP3 playing CD changer emulator for American Fords, circa 1995 to 2004. Those used an optional 6 disc changer unit, either in the trunk or in the console between the front seats. Some of the later models had a 6 disc in-dash changer, so this wouldn’t be for those.

    There are such things for newer Fords, and some other makes. How they work is they connect in place of the CD changer and on a Compact Flash or SD card have a folder for each disc slot. Up to 99 MP3 files can be put in each folder. Some systems will support more than 99 tracks per disc but don’t display track numbers above 99. Over 99 tracks is not part of the Redbook Audio standard.

    On the Ford changers, the stereo audio comes out of the changer as analog, sent to the amplifier. MP3 decoding, there are several single chip solutions to that. The thing to figure out is the control signaling between the head unit and/or amplifier and the CD changer.

    1. They do make aux-in -> CD changer adapters for the Ford Taurus, specifically for the 6-CD changer. I wish I would’ve known about them years ago when I got a 99 Taurus, instead of burning the tape deck up with a aux-tape adapter. But for the price and distance going from the trunk to front dash to connect my phone, I gave up.

      The majority of them usually have the standard AC/Heat knobs, which were in the same unit as the radio, so a third-party mounting system would fix it. Those with the digital climate control system were pretty much stuck with that or the final option. (4th gen Tauruses had a digital climate control bracket available from Metra, but go for $150+ nowadays.)

      The final option is to make an aux-in jack and hook it into the wires leading from the tape deck to the amp. I haven’t attempted it, but there’s a nice writeup of it in the link below.
      https://www.taurusowners.com/topic/2371-how-to-adding-aux-input-to-factory-radio-1996-07/

      Ford likes to be complicated on the minor things.

    2. I have a ’98 Buick Regal, and I’ve wanted to cook up the same thing for it. The only aux input the head unit has is for a factory trunk mounted CD changer. If I could find a way to connect it to my iPod or Android phone, that would be great.

  5. My 1996 Solectria E10 has a stock radio, with cassette tape player…
    I have always wanted to modify it to use Bluetooth and have a Qi wireless charger pad, and the magnet that enables Android Auto mode…

    Then I just insert my cell phone into the cassette tape slot and it connects and starts playing. ;D

  6. I sort of ‘built’ a radio for my last old car. I put that in quotes because it’s not like I was doing any circuit design or anything but everything was modules off of Deal Extreme.

    I had a Bluetooth receiver/FM tuner/SD Card – MP3 player module, a four channel amplifier module, and a 5 volt DC-DC power supply module. The 5V supply was for a couple of USB charging ports which I embedded into the faceplate. I also had a big relay fed by the accessory line turning on and off a nice fat power cable I ran directly to the battery which I used to power the stereo, a ham radio and the accessory socket. I had a toggle switch on the front to bypass the relay if I wanted to risk my battery charge and run stuff when the car is off and without using my keys. I miss that, it was convenient!

    Anyway, yah, the FM reception sucked and there was no AM. I almost exclusively listened to Pandora via Bluetooth anyway so neither of those things mattered except on really long trips when I got bored and wanted something I could tune around or when I wanted to listen to those automated low power local expressway traffic reports they broadcast on AM here in the US. Waze on my cellphone was more useful anyway so no real loss.

    The base of the radio was a piece of mdf scrap. The modules were all screwed down to it and I put a terminal strip on the back for easy hookup. I made a front plate out of wood and acrylic using a laser cutter. It actually matched the dashboard pretty good!

    I miss that radio. I think my wife would have a heart attack if I installed it in the new car though. The new car has an aux in port but I hate having an aux wire hanging out of my dashboard all the time. I miss bluetooth. I miss my accessory line that I could turn on w/o the key too. One of these days I will start building a Pi powered radio and once that is ready she doesn’t get a choice!

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