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Mercedes charging issue

Hello Car Talk Community,

We have a 91 MBZ 500 SEL with 189K miles. Recently we replaced the battery, and still, the battery drains. We took out the alternator, had it tested, and it tested fine. Now we are wondering if the ground wire is the problem.
Any ideas or similar problems out there?

The problem may not be charging, but a parasitic battery drain. Someone will have to do some detective work with a multimeter. Here’s how:

Thanks Jesmed - will investigate.