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View Full Version : Battery? Alternator? Power drain somehwere?



Sulaco
01-20-2008, 08:04 PM
Been a while since I've browsed the forum, gents.
I recently rolled over 200k in my beloved 202. I'm actually almost at 210k now.
I changed the FACTORY ORIGINAL fuel filter at 208k. It was a fun experiment seeing how long I could go and get away with it :)
Needless to say, boy what a difference it made in performance by changing that mofo. After I got the old one off the car, I poured its contents onto the ground (which were solid black liquid), and threw a match into the puddle.
It put the match out! Somehow my car was running off this for god-knows how long.

Anyways, my problem...
It's acting as if the battery has become weak, which makes sense. The battery is 6 or 7 years old with about 150k miles on it. However, the car also runs like complete shit for the first 10 or 15 miles after I get it started. I get in, the interior lights are dim, and it bearly has enough juice to turn over and eventually start. Then, when I want to accelerate above idle it sputters and almost dies. Once I get it above idle, I've floored it a few times just to see. The RPM's climb, but VERY slowly and the car seems to have lost 100hp. But, once again, after about 10 minutes and the car has warmed up, everything runs perfectly normal and great.

This morning, she was too dead to start. Jumped it off, ran perfectly fine for about a half hour (even during the first 10 minutes when it's normally weak).

Personal experience and conventional wisdom say that if the battery is bad, the car will run perfectly well once cranked. Furthermore, that if the alternator is bad, it will still have power shortages (or even failures) after it is cranked. But given the symptoms above, am I having both problems? Bad battery AND bad alternator? Or is there some kind of short somewhere causing it to drain power while sitting overnight?

adamsry
01-20-2008, 09:09 PM
Sounds to me like time for a new battery and alternator regulator. You could attempt to borrow a battery charger check the fluid level in yours and replace the alternator regulator this could be an even economical solution.

Given the age of the batt you can get a MB screw u over original or a sears / pep boys alternative for 50% or less the cost your choice *wink* The alternator regulator is easy to get access to it is accessible from the bottom of your engine looking up drivers side on the back of your alternator the gizmo is held in by 2 phillips screws and slides out easy peezy and replace with the correct new one.

Kropf
01-20-2008, 10:12 PM
Congrats on 208k miles!

6 or 7 year old battery pretty much explains it. I'm sure your battery is near end-of-life. A parts store should be able to put a load test on the battery to confirm. (How about putting at least a general location in your profile?)

I imagine that during the first few minutes of running, charging the battery is sucking most of the 'juice' from the alternator. After the battery's charging slows down, there is more 'juice' for the running engine, etc.

Yes, there is some drain when the car sits unless you unhook the battery cable(s).

A voltage check would also help your diagnosis. (The more recent W202s can display Battery Voltage in the Climate Control Display, but I don't think '94 W202s do.)

OzC36
01-21-2008, 03:49 AM
Probably just needs an alternator regulator. They are dirt cheap and easy to install:

http://www.autohausaz.com/search/product.aspx?sid=j5h2ck55ld0vvh45qt5ca155&makeid=800016@Mercedes&modelid=1195488@C280&year=1996&cid=regulator@regulator&gid=4884@Voltage%20Regulator

Or maybe the alternator is stuffed. Rebuilt are cheapish and easy to replace:

http://stores.ebay.com/Eagle-Auto-Electric

And of course, the battery is approaching the end of its useful life anyway regardless of what sort of charge it has or has not been receiving from the alternator!

Sulaco
01-21-2008, 04:54 AM
Thanks for the tips, guys.

It's the 2nd battery the car has ever had, it's a duralast I got for around $60 (if I recall correctly).

I did put a new voltage regulator in the alternator about 2 years ago. It was sending TOO MUCH charge and blowing bulbs everywhere (including my high-beams - scary experience). And I agree, it was a very easy replacement.

Strangely enough, it started right up this morning...??

And by the way, my location is the Middle TN area--where used 202's sit on lots everywhere :(
Dealers still try to sell 1994/1995 220's and 280's for $10k. I've test drove a few that are in dire need of that infamous head gasket and/or wire harness replacement. I once got a dealer to drop $2.5k off the price of one just by explaining that I've driven one just like it for 8 years.