Hey guys, I just changed my alternator on my 1.8 (M271 I believe). The back ground of the story is that I bought my car a few months ago and the clutch in the alternator (alternator #1) was going out thus making an irritating clicking noise.

I let my friend who is a certified mechanic at Mercedes check out my car and he ended up changing the alternator for me when My car went in for the cam sensor recall. Now the alternator I bought was a brand new Bosch (alternator #2) and after he installed it, it may a loud whining sound everytime the car was on. The whine was loud enough where it was getting annoying...

Now I got another brand new Bosch alternator (alternator #3) and swapped out alternator #2 for alternator #3. Before I install #3, I checked it out and everything seemsed good with it, spun the pulley and it seemed to spin fine. So out goes #2 andin goes #3. Once I tighten the 4 bolts holding down #3, I double check the pulley and it was now frozen! It would not spin and I was baffled. I figured maybe somthing dropped inside and locked it up.

So I go to remove alternator #3 and the first steps I did was to loosen the 2 upper bolts. I decided to checked to pulley again and the sum b*tch was spinning free now! A huge WTF expression took over my face. So I tighten down the foward upper bolt and the pulley was still spinning free, I tighten down the rear upper bolt and the pulley locked up again, So I loosened it and it the pulley would spin!

So I'm not sure if this is part of the design or if something is defective!

If you snug the upper rear bolt, the pulley spins fine the more you tighten it, the harder the pulley is to spin. If you tighten the upper rear bolt all the way down, the pulley will lock up!

WTF????

So now I know why alternator #2 was whining, it was probably because that uper rear bolt was tighten down to much! That pisses me off because I could have saved myself a whole lot of time by just losening that upper rear bolt instead of having to swap out the whole alternator!

Any one else experience this? Or does anyone know if this is normal or not? It still confuses the hell out of my why it is like this!

 

Something is wrong - I guess that's obvious.

Are you talking about bolts (200) in this diagram? Was your original alternator a Bosch or a Valeo? You are obviously distorting something to cause this freeze up.

 

Thanks for the reply!

The alternator looks like this, the bolts do not cross both halves of the caseing, so there is no way that I'm distorting it. Still baffeled!!

 

I've heard the USDM 05 230s have Valeo and won't accept Bosch ones without trouble. Is this true? I read that somewhere on this forum but I can't remember where or who said it.

 

Was it here Matt?
https://mbworld.org/forums/c-class-w...yesterday.html

 

It is evident that the Bosch alternator does not fit properly. The only way one could seize the alternator is if something is being distorted - Think about it!

 

I had the same thing happen on my old one, I had the housing backwards.
Undo all 4 bolts and spin it around.

 

+1. My car did not accept the Bosch one and it needed the Valeo.

 

That does make sence!



Never thought of that. I guess I'll have to do this again!

So what happened when you had the Bosch in?