The voltage regulator on my 300E went bad and left me stranded (after killing a relatively new $100 battery) and I had to get a tow. Car has 90k on it, voltage regulator was the original one from the factory. The brushes on it were obviously uneven (one was half as long as the other) and consdierably worn down. I would advise anyone who has somewhere near that mileage to check the voltage regulator, or better yet just replace it as preventative maintenance. It only takes a couple of minutes and a screwdriver to change (on the older 300Es at least, where it screws into back of the alternator -- on newer MB models it is integrated into the alternator and is not sold separately). The dealer charges something like $80 for it but you can get it much cheaper from Fastlane ($30 for the Bosch one) and other net sources. Actually, I have an extra brand new voltage regulator for a 300E if anyone wants it for $22 shipped in cont. US (I ended up ordering two, had one overnighted after seeing how long it would take the first one I ordered to arrive).

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2005 Mercedes C230k sport sedan, 6 speed
1987 Porsche 924S - 968-engined track car

Measured my charge at idle and got 13.8v, I don't know if this is good or bad, so many different opinions abound

The open circuit voltage reading will be higher on a cold engine.

I was reading 13.8-13.9 with the orig. alternator while testing a cold system.

This began to fall off as time went on so I decided to replace the alt. before it died. I installed a Bosch AL166X(100 amp) vs. the std. AL66X(80 amp) and now see approx. 14.3 at start-up first thing in the am.

I just bought a 300e about 6 weeks ago...

after reading countless posts..i did the following .....changed all fluids (still need to do differential) changed voltage regulator... changed thermostat.

I also put in Sylvania Silverstars.. I didn't think the existing lamps were bright enough.

I consider this a must if you get one of these cars. I still have an odometer issue that I am living with