Jeff Austin

Hi All - Two days ago my 2010 e350 4Matic Sport wouldn't start. I have about 80k miles on it and I put a new battery in it last summer, so I charged it up and it started fine. Took it to autozone and they confirmed the battery was fine, but the alternator was failing the test. Called MB and they quoted me $1500 since the alternator was a wear item and it wasn't covered under my extended warranty. I've seen that the voltage regulator can be the issue, but I haven't yet confirmed.

I'm completely comfortable digging in and replacing the voltage reg if that IS the issue, but I can't seem to get a confirmation on the part number. I've seen a lot of posts about ideal voltage, but nothing about the voltage reg specifically.

Has anyone had similar issues, and if so, is it worth replacing the voltage reg? If so, what's the part number?

konigstiger

Definitive diagnose, pull fault codes using MB DAS.

Jeff Austin

Awesome. I'll see what I can do on the codes. Thanks for providing the diagram!

mnje350

Hmmm, Alternator a wear item????? Is your warranty through MBUSA? By that logic, I guess a power stearing pump is a wear item, wiper motor is a wear item, AC compressor is a wear item.

I had an MB warranty on an '08 CLK 350. Never had to pay for any repair except hydraulic cylinders. Lots in the cabriolet by the way. They covered everthing else. Including the alternator. And, they put a new battery in it.

I would push this issue with whoever sold you the warranty unless the alternator is specifically excluded from the definition of covered repairs.

mleskovar

Did you test the alternator output at different RPMs? If it puts out more voltage at higher RPM it's usually a sign of worn brushes. Alternators have brushes and they wear. Easy replacement. Alternators have diode bridges (voltage regulator) and they fail. Easy replacement. Usually the brush holder and diode assembly is one in the same and can be removed without taking out the alternator and checked. Look on your alternator and it's probably that black plastic box at the end held on with a couple nuts. Today's alternators shouldn't "wear out" at 80k miles and I also don't believe they count it as a 'wear' item. $1500 to replace an alternator is robbery. Clean your commutator (the part the brushes contact) with a soft brush and air hose. Or am I dating myself?