Right now, my R is being work on for PW pump replacement and lower ball joint replace at the MB indy shop. And at the same they check my battery which they said it "failed". The R still will start but sooner or later it will die (6 years batt). My question is, what would I tell them when I call to have my battery change when the R still starts fine. My point here is, so that I dont have to pay for the labor and just pay the battery. Right! Am I correct? Let me know, any suggestions.

You are right in thinking to call Roadside Assistance so you can save on the labor. What you may consider doing is just calling them and say lately your car has had a hard time starting and that you understand the battery's never been replaced before so you'd like Roadside to bring out a battery... If they insist you bringing in your car, just tell them you can't/ have them bring you the battery.

thanks man. I might just tell them that the R wont start and I need battery. And if they ask how did you know its the battery. weak start or low voltage. I dont know. We`ll see either this week or next might call them.

Just as an FYI the battery's located under the passenger front seat and it's sort of a headache getting the battery out. You need to put the seat all the way forward and up and then you reach onto the panel from the second row legroom area. Make sure when they remove the cover that they don't damage the tabs. In some extreme cases the seat may need to come out in order to change the battery.

I needed to pull the front passenger seat on my car for another reason but I checked on the battery since the seat was out. I did have a new battery (bought the car third or fourth hand earlier this year) and the cover that goes over the battery was all damaged. The person who replaced the battery simply yanked the plastic cover out instead of properly disengaging all of the tabs. Anyways, when we did have the seat all the way forward, it was such a tight fit to do the battery that your technician will have a fun time.

Please do post your experience when you have it done as I'm interested in hearing how Roadside will do it for you. But if you're not having any battery issues now you may want to wait until year 7. That's typically when I've had to replace batteries on my other Benzes.

Edit: Reread your first post and they said the battery failed their tests. So yeah, may be a good time to replace.

Thanks for the heads up. Will take note on that. Again, thank you so much. Happy Thanksgiving to you and your family.