bohaiboy

Replaced starter a few months back and all has been ok. Drove on Tuesday and no issues starting. Got in on Wednesday and wouldn't start. Clicking noise and something else. No warning lights indicating issues. Put a charger on the battery. Indicated only 25% charged. Charged for 1 hour now shows fully charged. Started today no issues. How can I determine it it is a battery issue or perhaps the alternator or something else?

Shadly1

Check your voltage while running. You should be getting 13.5-14.5v

Load test on the battery. O'Rileys, Autozone or Walmart will do it for free.

bohaiboy

Will take by today to check out. Fully charged battery last week and have not driven since. Battery is dead today. Oddly, with the battery dead, my trunk pops open and will close, but then pops open again. Is that normal for a dead battery?

mcypert

Not sure about the trunk... Do you have the separate starter batt? The smaller one under the hood... It will die with no warning what so ever, and the V4 doesn't last too long.

See this thread on a starter batt that fits:

https://mbworld.org/forums/s-class-w...placement.html

Regards.... Mark

bohaiboy

The one under the hood on the 2010 is the main battery as far as I can tell. Its fairly large at about 15" x 8" and then there is an auxiliary battery behind the dashboard. Am I missing something?

mcypert

No,,, The earlier 221's have a large batt in the trunk and smaller starter batt under the hood just for starting... I wasn't sure of the change year. Since everything except the starter is powered by the trunk batt, it's hard to tell when the starter batt is bad... That was the point I was trying to make, but doesn't apply to your MY.

Regards... Mark