E36 Engine Noise with Bluetooth Adapter

[Chebyshev]

I installed a bluetooth adapter into the CD changer port of my C43 radio in my '99 M3. It is this product:

https://www.ebay.com/itm/Bluetooth-M...item340a05faad

Works as advertised, except there's engine whine that varies with RPM. I've read this can be caused by a bad ground or something along those lines, but I'm not sure how to start diagnosing it. The power and ground come into the device through the harness included with it, straight from the head unit, so I'm not pulling power from some different source.

Any ideas where I can start to try to get rid of this noise?

[JZeke00]

I installed a bluetooth adapter into the CD changer port of my C43 radio in my '99 M3. It is this product:

https://www.ebay.com/itm/Bluetooth-M...item340a05faad

Works as advertised, except there's engine whine that varies with RPM. I've read this can be caused by a bad ground or something along those lines, but I'm not sure how to start diagnosing it. The power and ground come into the device through the harness included with it, straight from the head unit, so I'm not pulling power from some different source.

Any ideas where I can start to try to get rid of this noise?

I have the same part and the same issue. I’ve been doing searches but coming up short as well. I was looking at old posts about the GROM unit that was similar, and one owner had received a cable with a capacitor in line that solved it.

If there was a simple way to ground this box that would probably solve it, but I don’t want to crack it open just yet.

Maybe the box has to be isolated from the chassis? Mine sits behind the OBC on the console carpet, where did you mount yours?


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[Chebyshev]

Mine is sitting in the glove box with the wires coming down through where the glovebox light used to be (I took it out for this purpose).

Sorry for the delayed response, I just got the M3 out of the garage for the spring and the noise is driving me crazy again.

As for grounding the box, maybe cutting the ground wire in the harness and grounding it directly instead of through the head unit would change things? I'm shooting mostly in the dark here.

[MarcoZandrini]

Actually, grounding the box will create a ground loop which will cause more noise.

[Chebyshev]

Actually, grounding the box will create a ground loop which will cause more noise.

Thanks. Goes to show how little I understand this problem.

I'm willing to experiment, any ideas for where to start?