W211 charging system failing?
 

Hey forum! Familiar names from rebuilding a 95 E320, but the forum looks rather quiet..

Here we are in the insane 2020, and now my W211 E320 is having issues with the battery warning coming on momentarily, then it also shows the code, Low Battery, Electrical Conven. Unavailable, and will stay in this mode for a while and then returns to normal.

Just changed the serpentine belt and drive pulleys so its not this end.

I will put the meter on the battery and check charge levels which should be around 14 volts, and at 130K miles Im wondering if alternator brushes are due for replacement.

There are some errors related to the rear SAM and possibly a battery controller so if anyone has tips Id appreciate greatly.

How old is battery?

Most likely cause is a failing voltage regulator.

x2

And what usually fails is the brushes (they wear out). They are integral to the regulator (usually).

Usually this occurs at around 150K+ but that's just a rough estimate. It can sometimes be changed without removing the alternator from the car, but it depends on the specifics.

On the W211 E320 it's easier to just pull the alternator. There's enough room between the engine and radiator to slide out the alternator and do the work on a bench. The V8s and diesels are another story.

Yes, right you are guys. Found a very informative video and have the part on order for 37 plus shipping, brushes and regulator unit. And yes it looks like a removal on the alternator, not difficult. Fortunately still getting the 14 volt charge when checked, for now.. but it clearly lost charging and went into stop car message with bad alternator for a moment. Its due for new brushes. Battery is a 100AH replacement a couple years old.

Great advice as always!

Remember to disconnect BOTH batteries before trying to disconnect the alternator. I learned that lesson the hard way.

Good luck

I've seen this a million times. This all points to a bad battery. If the VR was failing the warning would come on while driving. The fact that the system returns to normal operation after a while tells you the VR is working......

Wonder how old the battery is. I've about come to the conclusion that if you can get 3 or 4 years out of a battery you have done good.