W203 C200 2001 19kmiles

I need to jump start my car everyday because the "electricity" gone.Battery & alternator tested fine.My mechanic still cant solve the problem yet.Can anybody help me?Thank you

How were the battery and alternator tested? Were they tested in the car using an instrument that just touches the positive and negative terminals? The kind that AutoZone will do for free? In my experience, these are not thorough tests of these components.

The alternator should be removed and placed on a testing machine which will spin it up to speed and measure not only volts, but more importantly amperage output. Similarly, a dedicated battery load tester will provide a more accurate test of your battery by simulating a deep discharge. I believe Autozone may perform these tests, but I'm not sure. Old-school type parts places which *tend* to have more knowledge will definitely do these. Napa and some local CarQuest places come to mind, depending on where you're located.

In my opinion, the in-the-car tests are just for rough overview but aren't very thorough. It's similar to the handheld code scanners which just give you a rough guide to start troubleshooting but don't really tell the whole picture.

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If it has the original batttery in it, I would replace that as a first step. Five years in a car that sits a lot is about all you can expect.

Len

I generally agree with your observation, but a load test could still rule out the battery. Why replace something that is perfectly fine? $$$

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Only because he is having electrical problems, the battery is approaching or has passed its useful life and not running a car much is hard on a battery. Batteries now often fail without warning even with passing a load test. Now if the electrical system was functioning properly, I wouldn't automatically swap it out after five years, but it certainly would be on my watch list. Of course, we aren't sure whether or not this is the original battery or not.

Len

I replaced the battery with the new one about 2 months ago.Not the original merce battery but with bosch battery.And about the alternator,my mechanic use his "computer tools" to test it.Thanks.