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  #1  
Old 08-27-2013, 06:51 PM
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E300 voltage?

Regular readers will recall that I'm dealing with a bucking/stuttering issue under light throttle conditions. One weird thing that happened was after the indy mechanic replaced the old battery, the problem went away for a day.

With that in mind, I turned on the diagnostic on the CCU while driving home from work and watched the voltage (#24). It sort of fluctuated between 12.7 and 12.9 with the A/C and radio on regardless of speed and whether the car was doing its bucking/stuttering thing. Other posts in this forum maintain that proper alternator output should be 13-13.5 volts.

Is this correct? Do I have an electrical issue? If so, how do I narrow this down?

Thanks,

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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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  #2  
Old 08-28-2013, 07:31 AM
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I'll drive the car tonight and see if I can remember to do the diagnostic thing and note the voltage for comparison.
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  #3  
Old 08-28-2013, 08:28 AM
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Much appreciated, this bucking/stuttering is driving me nuts. Still suspect its something with the flaps, but just covering all possibilities for now .
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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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  #4  
Old 08-28-2013, 08:40 AM
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Your voltage regulator for one thing needs replaced as you should be getting 14+ volts to the battery. There may be other issues as well.
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  #5  
Old 08-28-2013, 07:56 PM
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OK - checked the voltage at the battery terminals - 13.1 to 13.4 V at idle - so I guess I'm OK. I'm surprised it's so different than the CCU, which was reading 12.6-12.9 at the same time.
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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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  #6  
Old 08-29-2013, 12:28 AM
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It would still be a good idea to check the regulator, especially if you're a fairly new owner and don't know how old the regulator is. Given that your IP is fly by wire, voltage variations could be causing your bucking problem.

Jeremy
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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #7  
Old 08-29-2013, 10:23 AM
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Thanks. How do i check the regulator - attach leads to it and start the car, look at the voltage? I admit I don't know much about diagnosing it.
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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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  #8  
Old 08-29-2013, 11:44 AM
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Regulator

Quote:
Originally Posted by VW1300 View Post
Thanks. How do i check the regulator - attach leads to it and start the car, look at the voltage? I admit I don't know much about diagnosing it.
You've done about as much as you can electrically. Next step is to remove the regulator from the alternator and see if the brushes are worn down to where they're barely making contact with the slip rings. You don't have to remove the alternator from the car but you do have to get underneath and remove any belly pans that may be in the way. Regulators are not expensive -- maybe $50 depending on the source.

Jeremy

EDIT: The photo shows a new regulator, left, and an old, worn (but still working) regulator on the right. As the brushes wear more and more, the springs can no longer push the brushes tightly against the slip rings and charging voltage is interrupted. Since your 1997 E300 is more electronic than earlier models, it requires a good, stable source of power. An alternator that is cutting in and out due to worn brushes or other problems could cause the stumbling you've been experiencing.
Attached Thumbnails
E300 voltage?-regulators_30920.jpg  
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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Last edited by Jeremy5848; 08-29-2013 at 11:56 AM. Reason: Add photo
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  #9  
Old 08-29-2013, 12:00 PM
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I'm not sure about the 97, but changing the voltage regulator on my 95 was a snap. I used a regular length screwdriver. How often can you do that?
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  #10  
Old 08-29-2013, 01:40 PM
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OK, will check regulator - probably Saturday morning - will report back any findings.
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Charlie

---------------------------
'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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  #11  
Old 08-31-2013, 04:58 PM
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UPDATE: Replaced regulator while I was there, car now charges 13.7-13.8V at idle, so I felt pretty good about that. Took the car out for a drive on some errands and then out on the highway. Car drove pretty good on the highway at first, I couldn't get it do do the stuttering/bucking but then after a few miles it came back. First at 2400 rpm, then over more of a range of rpms. This is similar to what happened 2 weeks ago after the battery was replaced.

Twice now the electrical system has been messed with and the problem seemed to go away briefly, but I'm still scratching my head over what that means.
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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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  #12  
Old 08-31-2013, 06:11 PM
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Charge!

Quote:
Originally Posted by VW1300 View Post
UPDATE: Replaced regulator while I was there, car now charges 13.7-13.8V at idle, so I felt pretty good about that. Took the car out for a drive on some errands and then out on the highway. Car drove pretty good on the highway at first, I couldn't get it do do the stuttering/bucking but then after a few miles it came back. First at 2400 rpm, then over more of a range of rpms. This is similar to what happened 2 weeks ago after the battery was replaced.

Twice now the electrical system has been messed with and the problem seemed to go away briefly, but I'm still scratching my head over what that means.
The charging voltage is about right (depending on alternator size -- if stock, should be 90 Amps). Perhaps the stuttering problem is not related to the electrical system at all.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #13  
Old 09-01-2013, 09:37 AM
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There is another relay that is at fault with cars 96 on. I think it is called k-10 but I can't remember exactly. It is on the passenger side near the front of the motor. It is long and has lots of electronics in it. Anyway it is a common fault for this problem. I think they are about $100 to replace.
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  #14  
Old 09-01-2013, 11:20 AM
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K-40 Module

Quote:
Originally Posted by ohiomike View Post
There is another relay that is at fault with cars 96 on. I think it is called k-10 but I can't remember exactly. It is on the passenger side near the front of the motor. It is long and has lots of electronics in it. Anyway it is a common fault for this problem. I think they are about $100 to replace.
The K-40 module has indeed been known to be troublesome. It lives in the black "This is not the battery" box on the right side of the engine. VW1300 you might consider replacing it if nothing else works.

Jeremy
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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #15  
Old 09-01-2013, 01:14 PM
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I have done a lot of forum searching and reading up on this issue - number one cause of stuttering/bucking seems to be resonance flaps, but indy mechanic says they're functioning OK. I've not used him before (came recommended, does enough MB work to have a StarTek system, and I've seen plenty of W123s and W124s at his shop) so I have to take that observation at face value. Also no codes thrown, as malfunctioning flaps tend to do on a '97, but some guys with flap issues have reported that codes were not thrown for them either.

Regarding K40 - from everything I've read when they start to get flaky, they cause stalling at highway speeds, failure to start randomly, and some other weird issues until they die completely and the car is stranded. Gasser MB owners with bad K40s have reported poor throttle response though, so it's not out of the question. I've been looking at the voltage regulator, fuel filters etc first. BUT now that they've been eliminated I'm willing to roll the dice on the K40. Besides, from all the K40 posts I've read, they're handy to have in the glove box.

I did a search on Pelican Parts for K40 relay, but don't see it. I suspect it's not officially called that - is this it ?

1997 Mercedes-Benz E300 Sedan - Switches, Motors, Relays, Fuses & Wiring - Page 3 The "relay module" P/N 210-540-03-72-M56

Thanks to all to responded - this is driving me crazy!

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---------------------------
'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)


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