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Old 05-01-2019, 04:44 AM   #1
Powling
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Continental VDO: Audio Slowly Fades to Nothing...

I'll start off by saying that I am really bad at understanding car audio - it might as well be wizard sorcery to me. That being said, I recently replaced my OEM head unit with a Continental VDO unit (with lots of help from mike.bmw!) and everything seemly works great, until I drove the car for more than 15 minutes for the first time since installing the unit.

I noticed that the sound quality slowly became static and scratchy, and the volume level faded quieter until it got to a point where I had to turn the stereo off because I couldnt hear anything at all.

What could be the cause of this? Its worth noting that my car had a 100% stock original stereo and wasn't modified at all throughout its life. So I'm not dealing with any bogus installed aftermarket wiring or anything like that.

Thoughts?
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Old 05-01-2019, 10:01 AM   #2
earthwormjim
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Do you still have common grounding? Modern head units do not like the grounds (- connection) all tied together. If you still have common grounding, the head unit might be overheating and throttling, that would be my guess.

Get a multimeter out, and check to see if left speaker minus has continuity with right speaker minus. If you don't have a multimeter, go buy one, you can't trouble shoot electronics without it.

It would also be good to monitor voltage as the radio fades out. You can measure voltage at the glovebox flashlight charge connectors, that gives you a rough idea what the radio is receiving.
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Old 05-17-2019, 06:06 PM   #3
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Originally Posted by earthwormjim View Post
Do you still have common grounding? Modern head units do not like the grounds (- connection) all tied together. If you still have common grounding, the head unit might be overheating and throttling, that would be my guess.

Get a multimeter out, and check to see if left speaker minus has continuity with right speaker minus. If you don't have a multimeter, go buy one, you can't trouble shoot electronics without it.

It would also be good to monitor voltage as the radio fades out. You can measure voltage at the glovebox flashlight charge connectors, that gives you a rough idea what the radio is receiving.
Boom! I finally got around to looking into this tonight and I think this solved my issue. I need to go for a longer drive, but playing through bluetooth for 20 minutes in my garage and the issue seems to be fixed.

I had both white wires as common ground with the head unit single ground wire. Figured out which white wire was the right one to connect with the head unit ground and everything seems to be good.

Thanks! I'll report back if the issue comes back...
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Old 05-21-2019, 06:57 AM   #4
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Update here:

The volume fading issue has definitely been solved, but now two other issues have come up.

Issue #1: After some time, the speakers seem to develop some distortion / crackling. I suspect this is due to the speakers themselves being the original ones that came with the car and have never been replaced? Thoughts?

Issue #2: I've noticed a whining noise coming from (what seams, but doubtful) the engine bay...this whining noise directly correlates with the RPM of the engine, and goes away when the car is stationary at stop lights for example...but here is the weird part...the whining noise GOES AWAY COMPLETELY if I turn the head unit off. What the hell would cause this?!
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Old 05-25-2019, 02:43 AM   #5
george graves
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All of this is grounding issues. Like classic grounding issues.
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