This is my neophite post so forgive me. I have an '05 C230 Kompressor that when I 1st start it and am in drive at a red light..the RPM's will dip almost 200 like it wants to stall then back to 800 and dip again. To top it off my radio and/or A/C will turn off for a couple seconds sporatically. I read some threads on here and thought it was my Alterrnator, I took it to my mechanic and my battery was going and straining my alternator.

I read about a recall on 2005 like mine that had the same problem...it's probably too late to take it to the dealer to have it fixed on the donut? I bought my Benz a little over 3 months ago.

Any help or suggestions would be greatly appreciated.

 

sounds like your alternator.

 

I thought that might be the case. I have a Valeo in there now and mechanic made some calls and parts are hard to come by to rebuild. I asked about a Bosch and he said I needed to rebuild or replace with same make of alternator. Does that sound right?

 

Yup, it has to be the oem Valeo. It won't take a Bosch one. I heard (do a search) that AutoZone actually sells the Valeo one.

 

It’s easy enough to have a battery and alternator load test performed to locate the source of your troubles.
Murphy’s Law dictated that both be recently replaced on mine.

Valeo for Valeo was required, although a competent independent automotive electric outfit remanufactured the works for a pittance.

 

I am hearing a lot of conflicting opinions on the Valeo or Bosch when Valeo is OEM. "Valeo seems to have more trouble than most of the other OES" - Will my car not run on a Bosch BOS1793744?

The only Valeo's I can find are on eBay

 

Yes, your car will not run properly on Bosch. My mechanic attempted to put the Bosch one in my car and my car did not accept it. It was running very rough and not idling properly. The Valeo one is the one that you need to go with.

 

I am not as handy or set up to work on my car like a lot of the guys on the forum. I've read about the Idler and Tensioner and don't know how to load test the alternator. Can I get the alternator load tested by AutoZone? Idler and Tensioner worth looking into? Thx - JB

 

I actually don't really know of many w203's that have bosch alternators I think i have seen one on here with one. My valeo alternator is at 165k without an issue so they can last awhile. If you live in the USA i have seen valeo alternators at places like rockauto, advanced auto parts, napa, autozone just check and see RMERUOPEAN is also good I order all my parts from them.

 

In South Africa Bosch alternators are frequently substituted for Valeo units with no trouble. In fact a member of this board has his US W203 in Tanzania & suffered a Valeo failure. We got him a new Bosch from Sandown Motors (owned by MBSA) & he dragged it back to Dar es Salaam as cabin baggage & all is well.

We have a Bosch plant here.

I wish I understood why people have trouble doing the swap. Maybe some Star coding/adaption required. It is afterall just a 12 volt alternator & regulator.

 

Pardon my ignorance. I don't understand the following "car won't accept Bosch alternator, only Valeo alternator". What does that mean? As long as the alternator is functioning properly (pulley spinning properly and the voltage regulator is regulating appropriate voltage range), then the make of the alternator shouldn't matter. Unless the voltage output of the Bosch alternator is 'outside' the acceptable range...then I can understand.

 

You & me pcy. And the Bosch alternator cerainly fits physically. If it doesn't it is 180 degrees out.

 

Alternators are not what they used to be,
The difference is in the voltage regulators
there are 3 variants MFR (multi function regulators)
LIN (local interconnect bus)
BSS (bit synchronis bus)
BSS and LIN are used depending on the engine ECU type
either ME2.8 or SIM4, these regulators actually communicate with the engine ecu and transfer infomation between each other, the engine ecu has control over the alternater to be able to control the torque loading for emmision requirments.
So you cannot swop an alternator with a BSS regulator with one with say a LIN bus. no communication will take place. that is most likely the difference between the bosch and valeo

 

Wow, thanks Russell . Its becoming complicated. Surely Bosch manufacture all 3 . You just have to select the correct one.

 

Thanks Russell. That explains it. Sandown wanted the exact Valeo model. They assured us that the Bosch supplied would work & it did. So one just needs to assure like for like.

It does not answer the "It was running very rough and not idling properly" unless the vehicle was running on battery alone at low voltage.

With Sunil scarce these days we need Russell.

 

I doubt that low voltage would make the engine hunt, usually its a mixture control problem like airmass TB or airleaks, one would need to hook it up to star and take a look at the live data, especially the mixture adaption values.

 

My idle would surge between 750 and 1k or when going above 40 in neutral (6spd) it would idle at 1.7k. My command head unit would cut out as well. Auto zone tested and said I had a bad battery. Spent $150 on a new mercedes batt and still had the idle issues whenever the temperature was below 75 deg. 6 years is good for the original Battery though so I wasnt upset to change it.
After reading several posts on here learning about alternator issues I decided to change mine today. On startup of the A/C or a near stall, I would get a noise from my accessory belt. I had read the alternator pully is the cause and this can damage the A/C compressor which was the last thing I had fixed this spring when my warranty ran out. There are several good diy's on here for the alternator change. Even in Atlanta it was hard to find a Valeo but I did for $180 for a rebuilt from O'reilly auto parts. Noise is gone and idle is perfect!
I did order new idler and tensioner pulleys and a new belt from an online merc dealership. The pulleys didn't feel great and after 105k the belt shows a little cracking. Local dealerships wanted $90 for the belt I got it for $50 shipped using online and saved half on the pulleys too. Get to play some more when those parts come in.
I was surprised how important the alternator is in regards to the idle.

 

Should I try replacing the Volt Regulator..I read that 04/05 Valeo's in the W203's had a "bad batch" of VR's? I found on for about $80...or just anty up for a new alternator?

Do I have to remove the alternator to find the part number if I just want to get a new Valeo Votage Regulator? Thanks again - JB

 

So I have started experiencing this problem over the last 2 months. Is it bad that i have not changed the alternator yet? is this something i should be able to by myself? I generally only change the and add more fluid on my car.

Any help would be great.

 

Not to sure if it's bad, but it may start causing other issues. I have now been thru 2 Valeo alternators in my car. I am pretty handy and there is no way I would at changing it myself. Find a local mechanic that works on imports and stay away from Benz dealership unless you have a warranty.

 

How much does the job usually cost? I saw on pelican parts a new alternator is around 400 bucks