diagnose: alternator/generator noise - replace?
Thread Starter
Almost a Member!
Joined: Jan 2008
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From: Germany
MB E420T
diagnose: alternator/generator noise - replace?
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!
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!
MBWorld Fanatic!
Joined: Dec 2004
Posts: 3,063
Likes: 27
From: Tampa, FL
2005 S500 4-Matic, 1978 450SL
If you have no radio installed, but rpm-related whine is coming through your speakers, then it is a grounding problem being picked up by your amp or by a component connected to it.
It could be a bad ground in the wiring to your amp, a bad engine/chassis ground, or a bad alternator ground.
The ground wires should be checked to see that they are not disconnected, damaged, or that there is no corrosion at the connection points.
I would not replace the alternator without trying those less expensive measure first; a new alternator would give you the same problem if the source was simply a poor ground.
It could be a bad ground in the wiring to your amp, a bad engine/chassis ground, or a bad alternator ground.
The ground wires should be checked to see that they are not disconnected, damaged, or that there is no corrosion at the connection points.
I would not replace the alternator without trying those less expensive measure first; a new alternator would give you the same problem if the source was simply a poor ground.
Last edited by Skylaw; May 18, 2008 at 12:31 PM.
MBWorld Fanatic!
Joined: Dec 2006
Posts: 6,500
Likes: 336
From: Europe
223.168 & 213.012 & 906.633 & 214.005
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!
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!
Thread Starter
Almost a Member!
Joined: Jan 2008
Posts: 47
Likes: 0
From: Germany
MB E420T
skylaw / Diesel benz
thanks for those helpful inputs!!
i checked the mass before and it should be fine (again, car hifi pros reconfirmed also)
the problem was there without any amp in between HU and speakers as well
the problem remains when changing hu
to me, it really seems like the input problem comes through the iso connector from the car, gets amped slightly by the hu, and then, if i also connect amps, even more by the amps.
i also added a capacitator, but that did not change anything (ie, before or after). however, there i have a voltage readout. i'm no electrician, but: is the voltage supposed to be a constant (when radio not on but got the remote on signal). eg, at 12.6V ? mine fluctuates, and is often above 13V as well, or is this perfectly fine?
appreciate the help guys, as said; i pretty much tried everything to no avail, and i am getting pretty tired of all the time spent on the issue.
i spend a lot of time driving and need to enjoy my music
thanks for those helpful inputs!!
i checked the mass before and it should be fine (again, car hifi pros reconfirmed also)
the problem was there without any amp in between HU and speakers as well
the problem remains when changing hu
to me, it really seems like the input problem comes through the iso connector from the car, gets amped slightly by the hu, and then, if i also connect amps, even more by the amps.
i also added a capacitator, but that did not change anything (ie, before or after). however, there i have a voltage readout. i'm no electrician, but: is the voltage supposed to be a constant (when radio not on but got the remote on signal). eg, at 12.6V ? mine fluctuates, and is often above 13V as well, or is this perfectly fine?
appreciate the help guys, as said; i pretty much tried everything to no avail, and i am getting pretty tired of all the time spent on the issue.
i spend a lot of time driving and need to enjoy my music
MBWorld Fanatic!
Joined: Dec 2006
Posts: 6,500
Likes: 336
From: Europe
223.168 & 213.012 & 906.633 & 214.005
What kind of a capacitor did you try? Where did you put it?
There are two known interference issues particular for this car. One is the CAN bus interference when the CAN bus wires are located too close to sensitive wires like the antenna coax. But I understood you having interference not only on the radio but like for the CD too.
The second one is that big capacitor at the terminal block.
Where did you measure the voltage? It may be quite different at the HU input from that of the battery poles. Fluctuations as such would not be an issue for audio quality, you would have to watch after audio frequency noise, preferably with an oscilloscope.
There are two known interference issues particular for this car. One is the CAN bus interference when the CAN bus wires are located too close to sensitive wires like the antenna coax. But I understood you having interference not only on the radio but like for the CD too.
The second one is that big capacitor at the terminal block.
Where did you measure the voltage? It may be quite different at the HU input from that of the battery poles. Fluctuations as such would not be an issue for audio quality, you would have to watch after audio frequency noise, preferably with an oscilloscope.
Junior Member
Joined: Nov 2005
Posts: 46
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From: South Florida
2010 CL63 (was 2003 CL55)
Me too !!! 2003 CL55
I have the same problem when I plug my SatRadio into the lighter for power. When the SatRadio is running off its' internal battery, no bleedthrough.
Also, when I use a power receptacle with the SatRadio in my 2000 Toyota Tacoma truck.. there is NO bleedthrough. ONLY with the Mercedes. Bummer.
Also, when I use a power receptacle with the SatRadio in my 2000 Toyota Tacoma truck.. there is NO bleedthrough. ONLY with the Mercedes. Bummer.
