Last week, I was driving my 2002 E430 and the BAS/ESP/ABS lights came on, the dash lights went dim, the accelerator quit working and after shutting the car off it would not restart (it also threw a Battery/Alternator malfunction).

I had the battery replaced by roadside assistance (since the battery was original with the car) and everything seemed to be in order.

I drove it 3 or 4 times over the weekend and everything worked fine... However, today on my way home from work I had the same problem (lots of malfunctions and eventually another dead battery).

When the car was running - I did not receive any alternator/battery warnings, however the car won't turn over now.

To me this seems like an alternator or voltage regulator problem. I'm looking for advice on the best way to test either/both...(or ideas on what the problem could be otherwise).

Thanks!

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE