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Discussion Starter #1
Was driving home last evening and had the battery warning light come on in the right side of the dash of my 2002 SLK 320. I immediately feared it was my battery failing or similar and being that I was only 3 miles from my house drove it home. Upon placing my voltmeter on the battery, I got 11.4 volts with engine off and after cranking it back up only was see 10.8 volts while the car was running (red flag).

After verifying in the manual that the warning light that looks like the battery was more or less a dumby light for anything in the electricaly system, I immediately took her the 6 miles backup to my mechanic. -- I did have to stop and buy them all a box of donuts along the way, which allowed me to stop and start the car once more.... which helped to confirm the problem when I got to the shop and the battery was only showing 9.6 volts.

Upon arriving at the shop, I was greeted by three very hungry and happy mechanics which then all jump onto my car and confirmed that in fact my alternator had flacked out.

Now, my generous attempts at humor and bribery asside... I was not happy to be spending another $350 for a replacement alternator so soon after only last week spending $400 on a leaky valve cover, but I did buy this car used and prior to the dealer doing any major servicing.

Long story out of the way; are there any issues with SLK's or the Merc 3.2l engines eatting or chewing up alts more frequently than others? or can I be confident that this is simply a result of age and one of those routine things that does and will go wrong if given enough time and usage?
 

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You did not indicate the mileage. Some items are wear related and others tend to be age related (rubber seals, etc). I have a 1972 MG with the original alternator working fine, but it only has 48,000 miles. On the other hand, I have pretty much replaced every hose and belt more than once and lots of rubber parts. I recently purchased a 2001 SLK320, so we are in the boat together. Good Luck!:)
 

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Discussion Starter #3
Sorry, 81,000 miles on my 320. My mechanic is pretty nonchalant about the whole thing. he deals a lot with Porsche's and similar, that will sit around for years on end and then get sold to a new owner who takes it from a weekend outlet to a daily driver and by simply driving it more, and differently than it had been can bring to light issues that either would have popped up long ago on a regularly used car.

I suspect this was nothing more than something along those lines and haven;t found any evidence about MB alternators of one year over another being an issue, but figured I would ask around.
 

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Because an automotive alternator is "open" for cooling they are prone to dirt, there are many mechnical moving parts and electrical parts that are susceptible to heat, and the load varies based on demand from accessories etc, it is almost impossible to arrive at a typical life span. My daily driver cars are the only ones I have replaced an alternator and typically after 250,000 miles. Since the vehicles have such high mileage I don't buy new alternators, I use a local rebuilder. When I put the question to him as far as typical alternator life he said it is unusual for a failure to occur under 50,000 miles. He thought the "average" is about 100,000 miles but lots of cars run 200,000 miles. He also mentioned that failures are not prone in any particular brand.

PS I have an automotive alternator in a marine application and that alternator must be sealed (no sparks) and the rebuilder expects the life to be halved due to poor cooling.
 

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Before I purchased My SLK, I spent quite a while researching SLK 230 and 320 issues. Like you I never heard alternator mentioned. Just one of those things.......
 

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I wonder if it was just the brushes on the $33 voltage regulator and not the alternator that went bad. That would have been the first place I would have looked. Two screws to remove it and a fifteen minute job.
 

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Discussion Starter #7
well, its done, gone and money spent now. But I can scratch that off my list of things to check, as I get to know this car. I created a punch list based on what I read, learned and already knew about these cars. This was the first and so far only unexpected issue to arrise, so hopefully I am lucky.

Next on my list, a tranny service, then on to my suspension (don't ask, someone put aftermarket KYB's on the car), then I want to go through the entire top system and make sure it has the requisite service done. All in all though, I am counting on some of that bullet proof build quality to still be there even after 11 years.
 
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