OEM Cellular Phone Revival, Bluetooth Integration

[pointblank9957]

Hey Guys!
Ever since I purchased my first urS4 and discovered the cellular phone in the armrest, I've always wanted to see if I could bring back its functionality. Well, using the brain from other Bluetooth handsets, this is totally possible. As of right now, the keypad is inoperative, but maybe that will change down the road. Using the internals from a Bluetooth earpiece, you can bring back functionality of the OEM phone. The car this is going into is a 1997 A6 Avant Quattro. This car was not optioned with the cellular phone, but the phone jack is indeed still there. I swapped the entire armrest from my old urS4 into the A6. I'm not 100% if power is still supplied to the jack, but this is easily corrected if not. Just run a ground to the Brown wire, and power to the red and blue wires to power the Bluetooth & keypad lights.

Parts needed:
Bluetooth Earpiece
Buck Converter 12v>3v
Wire

Tools needed:
Soldering iron
Wire Strippers
Wire (I reused wire from the loud speaker)
Various torx bits

Step 1:
Disassemble your phone, there will be 3 torx screws holding the case together.

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Step 2:
Snip or de-solder the wires for the Speaker, Microphone, and Side Switch. These will all be soldered to the Bluetooth Earpiece's motherboard. The Switch will be used to turn on and off the earpiece's motherboard. In my case, this button when held for a second activates Siri on my iPhone as well. The speaker is held in by double sided tape, I managed to remove it and turn it to save wire. I even reused the tape!

Step 3:
Prep the Earpiece's motherboard for retrofit. Snip or de-solder the speaker & battery. The mic in this case needed to be snipped off completely as it is a surface mounted component.
Red: Speaker + & -
Blue: power + & -
Yellow: Mic + & -
Purple: Switch + & -

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Step 4:
Prep the power wires and buck converter. The brown wire on the phone jack is a ground, the red and blue are both power wires.

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The Buck Converter has a + & - input and output.

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Step 5:
Solder in all the components to their pads. In my case, all the pads are labeled on the earpiece.

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Step 6:
Secure the motherboards for the earpiece and buck converter to the phone case with hot glue or double sided tape.

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Step 7:
Reassemble your phone, pair your smartphone to the earpiece once powered. Depending on which earpiece you buy, you may experience mic distortion. This can be corrected by running a resistor on the + mic wire. This is trial and error. Somewhere around 4k Ohms usually does the trick.

[jbrentd]

Nice work! Thanks for posting this.

[JohnBarleyCorn]

Haha! Totally useless, but totally awesome. I wish I had kept my old aftermarket cellular that was in the Audi 100 I parted out, but I sold it to a NYNEX collector, so at least it’s still out there. Great job and great write up. Thanks!


Sent from my iPhone using Tapatalk Pro

[pointblank9957]

Haha! Totally useless, but totally awesome. I wish I had kept my old aftermarket cellular that was in the Audi 100 I parted out, but I sold it to a NYNEX collector, so at least it’s still out there. Great job and great write up. Thanks!


Sent from my iPhone using Tapatalk Pro

I just like keeping the original equipment working or adding modern amenities while maintaining the original look

[AustinEngy]

Great writeup! I’ll definitely have to do this!! Would be even cooler to find a way to get the buttons to work, but how often am I typing in numbers anymore lol. Doesn’t the factory phone also have some sort of loudspeaker option? Or does the external speaker only get used for the beep noises from the phone? I’m sure it’s in the owner’s manual.

[pointblank9957]

Great writeup! I’ll definitely have to do this!! Would be even cooler to find a way to get the buttons to work, but how often am I typing in numbers anymore lol. Doesn’t the factory phone also have some sort of loudspeaker option? Or does the external speaker only get used for the beep noises from the phone? I’m sure it’s in the owner’s manual.

The phone does have a loud speaker as well! There is a mic in the overhead console for the sunroof. As for keypad functionality, I may look into this, but I will need to find a compact Bluetooth set that has a keypad. That may be the difficult part. Maybe I can get lucky and find a landline with Bluetooth that can communicate directly with a smartphone without needing the receiver box. I may develop a PCB that can send all the button presses to said landline's motherboard. Maybe I can start doing this conversion under my Kujispeed business alongside my other projects I've done for the C4 community!