Sherlock

Came to this forum as my 2005 S55 is very similar to the E55. Car has original battery and has never skipped a beat. Today on freeway, the following mesage came up on my screen twice. ""Battery Voltage Too Low- Please start engine or command will shut down in ten seconds". Well, I was on then freeway going 60 mph so I igniored the note. It came up again and was present for 5 seconds or so, then the screen went totally black and audio turned off. The heat to my seats turned off and the red lights indicating the seat heaters are on began to blink. Finally made it to my destination, turned the car off and it would not start again...it tried but not enough juice. I know the battery is old, but have never had a problem. Alternator probs???? Mileage is 45K.

BBBSS

If its not the battery your alternators voltage regulator probably went dead. Fairly common on these for some reason. A replacement Bosch can be found online for about $45. It's an easy half hour install if your taking your time. Rarely is the alternator itself bad, typically just the voltage regulator.

If your battery tests good (parts stores will test this for free but you may have to pull the battery out for them) then I'd grab and throw in the voltage regulator.

Or you can send it in to the dealer and have them throw in a new alternator and get a bill for probably a $1000+ lol

AWOL

Ive had the exact same issue. Charge up the battery, see if it restarts. Put it in dyno mode and monitor the voltage if you get it running. I was getting 11.3 volts while running with a bad alternator.

BBBSS

Check out this thread.

https://mbworld.org/forums/w211-amg/...lternator.html

Sherlock

Unfortunately the car is now at a dealer in San Jose, CA as I was out of town for a meeting. Can I ask them to simply replace the voltage regulator if that is the failed component they discover??

BBBSS

If they do come back saying its the alternator you could mention that you have learned that its commonly just the voltage regulator and ask if it might save you some money to have just that replaced. Likely they will try to hit you with more diagnostic time or charge a lot for the regulator as they need to live up to their nicknames of being the "stealership".

Your best bet would be to get an estimate for repairs before they do any work, see what their diagnosis is, and see if they will work with you on the voltage regulator to try and save you money if that is indeed the problem. Be prepared to hear crazy stories of why you should just replace the whole alternator, they're likely to try and up sell you.

Sherlock

Spoke to dealer and it was the voltage regulator. $70 part plus labor. Good thing I have an extended warranty. Battery was on its way out and could keep it but will replace with new. It's 6 years old. Thanks fpor your feedback and advise. Happy Holidays!