Replacing Factory Radio with VDO TR7412UB-OR Head Unit

[depe30]

Previous owner of '91 318is had installed the OEM E34 radio, and I'm replacing it with a bluetooth-capable head unit. I decided on the VDO/Continental TR7412UB-OR for its clean, period-correct aesthetic.

Ordered these from ECS:

• VDO TR7412UB-OR Head Unit (ES#: 3427250)
• VDO Headunit Wiring Harness (ES#: 3619860)

Upon removing the factory head unit, the internal wires are twisted and electrical-taped together to the factory wiring harness wires. Much of the electrical tape is loose and melted.



I'll clean up this jumble of tape & wires by cutting and re-connecting each wire with heat-shrink butt connectors. I have a BMW stereo harness adapter (Scosche BW01B) on its way, so I can easily swap out to OEM unit in the future if needed.



Taking stock of the existing wire colors, I referenced them against the Pelican Parts article and VDO manual:



The "GAL" wire, which appears to supply speed signal for adjusting the volume based on the driving speed, will be unused in the new VDO unit.

I noticed the "Illumination" wire is missing in my configuration. Hopefully this is not necessary?

[depe30]

Completed install:



Noticeable improvement to volume/sound quality, and the bluetooth function works very well for Spotify streaming & phone calls.

[Cha Ching]

Looks beautiful in the dash. I'm sure many of us would appreciate some additional pics of it to show the period-correct look.

[depe30]

Cha Ching here's a photo from the front with illumination:

[nomalt]

Just installed mine today!

[No1b4me]

I installed mine this past weekend. I love it, really enhance the driving experience on the vert. With the stock unit, I thought I would have to replace the speakers as well cause it sounded so bad. As soon as I put in the new unit, the speakers came alive!!

Question for you guys, I didn't really screw it in per say, did any of you guys screw it in place? Or just push it in like I did since it fitted pretty good. Please let me know. Thanks.

[Powling]

I installed mine a while ago but am having issues with it ever since install. Basically it works fine for the first few minutes then slowing the quality fades to static in the first 10 minutes. It develops a buzzy static sound and is eventually unusable after that. Any thoughts?

[mike.bmw]

I installed mine this past weekend. I love it, really enhance the driving experience on the vert. With the stock unit, I thought I would have to replace the speakers as well cause it sounded so bad. As soon as I put in the new unit, the speakers came alive!!

Question for you guys, I didn't really screw it in per say, did any of you guys screw it in place? Or just push it in like I did since it fitted pretty good. Please let me know. Thanks.

I just pushed it in and pressed the triangle-shaped retainers on the metal sleeve outwards. That seems like a fairly reasonable and accepted installation practice.

I installed mine a while ago but am having issues with it ever since install. Basically it works fine for the first few minutes then slowing the quality fades to static in the first 10 minutes. It develops a buzzy static sound and is eventually unusable after that. Any thoughts?

That's odd. Do you have a factory amp? Is it being bypassed? I don't believe mine (another 318is) has a factory amp, but I'm not sure if other markets (Canada) received a factory amp on the 318is. I can't think of another reason, aside from a faulty unit, that would result in the issue you've described.

[Stan]

I installed mine a while ago but am having issues with it ever since install. Basically it works fine for the first few minutes then slowing the quality fades to static in the first 10 minutes. It develops a buzzy static sound and is eventually unusable after that. Any thoughts?

If you have a trunk mounted amp and it has gone bad, you may need to replace.

[earthwormjim]

I installed mine a while ago but am having issues with it ever since install. Basically it works fine for the first few minutes then slowing the quality fades to static in the first 10 minutes. It develops a buzzy static sound and is eventually unusable after that. Any thoughts?

Check your factory amp if you still retained it.

Also ensure you're not using common grounding for the speakers' "-" terminals. Each speaker "-" should be wired separately to each channel on this headunit, and not tied to chassis ground.
If you have common grounding on your car, you can just avoid hooking the "-" wires up to this headunit, and essentially have a floating "-", but you might have a bit of noise from the distributor/spark plugs.

[kangstaE30]

Thank you for this write up, depe30 ! it helped me tremendously in installing mine. I just completed install of the TR7412UB-OR last night into my 92 318iC with premium sound. Replaced an aftermarket Pioneer CD head unit that was probably installed 15 years ago, sounded good but no bluetooth and don't need CD player anymore. I thought I would share my experience in case it helps others.

I followed OP's diagram, but I took a chance and connected the Orange illumination wire to the internal "Red/Gray" wire that was waiting patiently in the dash. It was not connected to the Pioneer head unit beforehand. When I first installed before connecting orange to red/gray I got no illumination on the new unit when powered off, with headlights on or off. After connecting orange to red/gray, all of the buttons are illuminated (not the screen) when the headlights are on. Buttons go off when headlights are off. Similar to HVAC control illumination. So, it seems to work.

Caveat, I have not driven the car yet so if red/gray is truly the speed signal I am hoping it doesn't screw things up when driving. But it seems to be connected to the headlights, obviously, so I don't think it's speed signal (at least on mine). I Will report back if it catches fire when I accelerate.

Thanks again, OP.

[bradnic]

great job on this, especially figuring the wiring out.