Only Charging at 11.3 V
 

Hello - My '06 E350AWD is only charging about 11.3V while idling. I assume either the Alternator or Voltage Reg is bad. Is there a easy way to tell which one to replace?
Thx

What is the voltage at 1500 rpm

Hello - Thx for responding! I checked and got 11.3v at 1500rpm, 11.5v at 2000 & 3000rpm and 11.6v at 4000rpm (but it dropped back down to 11.4 or 5 after a few sec). BTW, At each step I was holding it for 5 sec or so without seeing any change. IMO, It is not charging, but I don't know if it's the alternator or the V.R. - thanks again for the help in deciding which it is!

Happy Thanksgiving!
Larry
06 E350AWD

Doesn’t sound like your charging at all. Not sure if the regulator is serviceable on that alternator.

Never mind I looked it up, it is. $40-$60
I’d probably just change the whole alternator and call it done

Thanks! Replacing the Alternator is likely the best option.

I will hopefully be back on the road again soon. Now, I have to find out how much trouble it is to replace. Normally, I wouldn't hesitate, but even with the plastic covers removed it still looks like a PITA. Oh well, it is what it is and I'm not in a hurry. (fortunately).
I'm sure DieselBenz will probably say the same thing. I won't order one for a couple of days just in case he says something entirely different (which I doubt).

Happy Thanlsgiving!

https://m.youtube.com/watch?v=C-gXaTezfpw

Doesn’t look too bad

On the diesel discussion a member pointed out the alternators use a Lin bus communications on these alternators. He had purchased a napa rebuild but the Lin bus was no good so he ended up buying a new MB alternator. I think I would change just the regulator based on his experience.

Thanks DieselBenz! BTW, I owned (and loved) a 91 300D 2.5T for years - it finally died from rust around the rear suspension but a fellow Forum member bought it and repaired it. I would have hated to see it go to the crusher. My present Benz (gasser) is certainly lacking in many ways.
Ok, so replacing just the alternator might do it. Hmmm.... I guess there's no way for the amateur to benchtest a VR?
Larry

It's the brushes that wear out. You need to remove the VR to inspect. The fact that voltage is low indicates a bad VR. You could get it tested free at some auto retailers and have your battery checked out as well.

Start simple first.....Also check the tightness of the belt. Though you would likely hear telltale signs of the belt- and the VR and/or alternator sound like the most likely, never just assume without knowing all possible failures that could cause such symptom.

Only Charging at 11.3V
 

But aren't the Brushes in the Alternator? Also it seems like your suggestion is 2 steps:
1. - check the brushes and
2. - check the VR.
What would I be looking for if I remove the VR and inspect it? Is it possible to test it with a DVM? If yes, please remember, I am a amateur when it comes to t'shooting via DVM. Keep it simple please.
Thx

The length of the brushes, new would be about 3/4 inch long, once they get to about 3/8" approx then time for a new VR. Voltage should be 14.1

Brushes are part of the regulator.

That is the VR note the carbon brushes are the wear items.

Thanks for the image and info! Excellent Info. BTW, can just the brushes be replaced? (just out of curiosity) ;-)