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MB E420T
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Discussion Starter #1
Hi guys,

in my E420, i keep having the noise coming from the alternator/generator (lichtmaschine in germany). it has nothing to do with false audio wiring install or what not, as checked by pros.
so, the problem is: even without a radio installed, i have the distortion sound from the generator/alternator meaning rpm dependent & hearing gearshifts, through the speakers. of course, linking up an HU only amplifies this sound.
the audio pros cant figure it out either, and mention i may have an electrical problem with the car itself.
Question to the forum experts: did anyone have similar issues? would replacing the alternator/generator fix the problem?
i am going crazy from this noise.....
thx for yr help!
 

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'01-E320 & 02-ST2
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Hi, KC.

I can't believe no one else wants to take a stab at this. :rolleyes:

I have never heard of this issue on a modern Benz. In the olden days this could be an issue that was resolved through capacitors. It seems like if it were something that could break in these we'd have heard of it before now.

Before you start thinking of changing the alternator, I would try disconnecting the plug in the back (not the main lead to the battery, just the plug-in connector). That will keep it from generating current and will let you confirm whether it is in fact the problem.

Also, if you haven't inspected the brushes, do that. Actually I guess if it fails the above test the next step would be to pull the alternator and pull the regulator (the brushes come out with it). If they are badly worn then I suppose that could have an effect.

If not, you can try the capacitor route; only thing is it's been so long since I dealt with this I'm not sure where it would go...assuming you can find one. ;)

Take care and enjoy the ride,
Greg
 

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MB E420T
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Discussion Starter #4
thx greg

jeffrey:
to be clear: i threw out the stock bose system, all of it, incl HU.
i installed new HU, with RCA links to 4 channel amp powering new 4 speakers in doors, plus 2 channel amp powering my sub (sure i separated the power & rca cables, left and right of car). i did system installs in my previous cars without any issues.
i know where u r getting with this, but i already checked everything.
1. the sound remains there without any amp connected
2. the sound is there when plugging another radio simply to the iso connectors.
3. when testing the speakers, they were connected first directly to the amp so it cant be the bose cable set either
4. i had car profis (install shops) check everything twice, but couldn't locate the issue either.
so, in essence, the distortion sound seems to be inputted from the car's connection, then amplified once by the HU, and once more by the amps.
i tried linking a distortion filter between car power input and hu but to no avail. took it back out and now it is even louder.... i am also getting the voltage pop sound when radio goes on. pfff
i am at the end here with this, so i turn once more to the forum. i mean, the car hifi guys (2 different shops!) checked the connections, they are fine. they then tell me the only remaining problem could be an issue with the car's electricity itself, leading me to the alternator/generator problem.

just one more thing: in between i also added a capacitator to power the amps (which made no difference to the distortion issue). i have a voltage readout there coming from the battery: is that number supposed to be a constant? ie, at eg 12.6V? because, it fluctuates and often goes up to 13 something etc. perhaps this could be a clue? i'm no electrician, so bear with me :)
appreciate the help guys
cheers
 

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98 E-320, 2003 E-500
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685 Posts
KC

Without being there, it's hard to diagnose, but I'll take a stab

Did you have the capacitor serially connected to the red remote cable (not the red power cable that goes to the battery) to the HU? The distortion filter as a fancier unit works the same way (floating ground). Does the filter looks like this:

American International S-15A / S-25A Power line noise filters at Crutchfield.com

Another thing to check is your grounding. Are you grounding it directly to the chasis?

Good luck
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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17,193 Posts
Hallo KC420,

I was about to suggest you post this on the Audio & Telematics forum too, but checked and see that you did. I also saw there are no replies to you yet.

Do not feel bad about that. I posted one simple request for error code interpretation and only received one reply from a guy who was curious about my problem but admitted he did not know what those codes meant. There may be knowledgeable people there, but they made no attemp to help me.

Anyway, Greg and Jeff are at least trying to help you here. Good Luck with the diagnosis and cure!
 

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MB E420T
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Discussion Starter #7
thx musimann, and others.
again, i had all the installed wiring (ground) checked by 2 (!) different pro car hifi installers... so that seems all right.
again, 2, i checked the system without any fancy stuff (ie, without connecting anything else than the standard hu to the standard iso plug), and the sound was there as well.
to me, it really seems like it is coming (input) from the car's electrical... then passed on through the HU into the speakers (amplified even more by... the amps of course).
why is that?
well, even if all audio is turned off, i also have the alternator distortion sounds... just less loud.
i just wanna make sure that, if i were to get a new (or used) alternator installed, it would in fact solve this problem.... which is, day by day, driving me more and more crazy...
some experts here want to keep me away from the nuthouse?
thanks ;)
 

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Just curious...did you try disconnecting the alternator and regulator to isolate it/them as the actual cause? I suggested that in the earlier post because it would only impact the sanity factor if you replace it needlessly.
 

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MB E420T
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Discussion Starter #9
hi gregs210
currently extremely busy period, and each time i would have time to work on the car it is after driving...so the engine bay is smokin hot (also have to check plugs etc)-
thx for the tip, i keep u updated once i find a cool moment.
cheers
 

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2000 W210 E430T4matic Brillantsilber met.
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Thats funny... I got exactly the same problem yesterday when installing almost the hifi setup. Im keeping the Comand HU for now...

Did you ever solve the problem ?

I fixed a bad ground connection at the battery (ground #1) and a bad ground connection at the antenna amplifier in the back... That reduced the hissing noise a lot, but I still have a alternator and a enginestart pop...

If it keeps on like this Im cutting of all the mufflers... :)
I like the options to drive in silence that the benz offers, so I prefer solving than killing...

-devi
 

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to Check Codes " in particular, but anyone else also.

What are the issues indicating if the Alternator is quite silent spinning on the drive belt as per normal,
BUT ONLY WITH WIRING AT REAR DISCONNECTED experimentally as you described,
so there is now no electric input or output?
So presumably as the Alt is spinning rapidly still engine-driven, and is then now silent, surely it cannot be the bearings as many clueless people are telling me, which I do not really believe.

When wiring is re-connected,so now everything is connected fully for normal functioning,
a low ghostly groaning whine/moan recommences which does sound like some electricity noise rather than a mechanical noise.
The old alternator I just had to replace after 10 years also made this kind of noise the whole time, except more severe, it would also often, at night, when I first switched on headlights, make the noise more intensely and put the alt warning red light on...this light would persist stubbornly until I switched lights on and off a couple of times, then the ALT light would go out and noise would lower in tone, but still be quite noticeable . Despite this issue that ALT kept working well enough to keep the vehicle going. Suddenly a few weeks back, driving in daytime, the charge light came on and stayed on for good,so that one was obviously finished now completely,
so I had to trot out another old dusty old secondhand ALT which I had spare.
It works, charges, it does not have the strange foible when lights are first switched on, but although far less loud, it TOO has a low electric-sounding moan when running.
When you experiment as you say,ie with rear wiring disconnected, so then there is no elecrical activity possible,
the ALT is that state, is then spinning completely silently, as one would desire at all times.

This moan never goes away when eng running at any time, even after running for several mins and battery has now been recharged after the discharge of the starting.
It is still working but moaning away audibly.

What issue/s makes this special kind of noise?
BTW, this vehicle is a base model Toyota light commercial pickup with ND electrics and external regulator.
 
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