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1992 500SL
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Discussion Starter #1
Hello all,

I've found in the WIS/ASRA that there possibly exists an active noise cancelation system in our cars. My car has the SA code 810, and through the WIS (Which refers to it as 97B) that this has a speaker and microphone system to cancel out the engine sound.

I have heard some sort of high pitch speaker tone coming from the back of my car, so I am taking a guess that this is the system, and it might need some work done (previous owner wreaked havoc on the sound system an aftermarket system, currently undoing the damage).

Does anybody know where the control module for this is, and where the microphones are located? Or really anything about this. The WIS refers to the 2018 model 177, so not super helpful.
810.JPG
 

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M113 SL500
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469 Posts
I think you're cross referencing too far forward/backward for your r129 with that tech sheet. In some models, 810 refers to newer Harman systems, some of which have active noise cancellation. Harman was never implemented in the R129.

If the previous owner screwed up the sound system, perhaps what your are hearing is alternator whine. Does the pitch change with engine speed?
 

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96 SL600, 07 BMW M5 ,04 545i sold, 2013 C300 Sport (for wifey) 03 CL55 s/Chg sold,91 500SL, sold
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112 Posts
I once changed the sound system on my 1991 500SL with a new in dash navigation unit and a subwoofer in the rear compartment. This sometimes generated a high pitch sound which was kinda subtle in a way but still obvious.
I got this corrected by adding a capacitor to the amplifier.
So since your radio has been changed you might be in the same boat as well.
Hope this info helps!
 

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M113 SL500
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469 Posts
I once changed the sound system on my 1991 500SL with a new in dash navigation unit and a subwoofer in the rear compartment. This sometimes generated a high pitch sound which was kinda subtle in a way but still obvious.
I got this corrected by adding a capacitor to the amplifier.
So since your radio has been changed you might be in the same boat as well.
Hope this info helps!
What you describe is alternator whine.

The proper fix is to properly ground your stereo system and make sure none of your components are faulty. Ie, pico fuses blowing on some older Pioneer stereos.
 

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1992 500SL
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3 Posts
Discussion Starter #5
brahaus, I believe that is the more logical explanation than what I had.

The whine doesn't increase or decrease with speed, just more obvious when at idle and its quieter. Sadly to get the audio system back to OEM, would require a total transplant from another donor- as very little remains. Maybe for next year. :)

Thanks all!
 
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