How to replace Auxiliary battery on a Mercedes S550 (w221).  

Hi bro, I apologize for the late response here. Glad to hear you found this video resourceful. Not a problem, thank you🙂.

Thank you. I am glad to hear you found this video helpful. Also, thank you for sharing that the 2012 SLK does not have the fuse panel there. I just learned something new from you! This might be knowledge for others as well 🙂

not a problem brotha🙏! Glad you were able to find this video! Yup if you are seeing this message on the dash, then switch the auxiliary battery from the video and that solves it.

Thank you so much! I’m glad you liked the video 😊.

Hi, thank you, I am glad to hear you liked how the steps in the video were demonstrated. Yes it seems that on some models the auxillary battery location is harder to get too versus on some its much easier. Thank you for sharing that comment. Happy New Year!.

Yea the trunk definitely would be more easily accessible vs under the steering column. Thanks for sharing with me!

Update switch auxiliary battery but fix issue. Benz are difficult

No you do not need to disconnect the main battery.

@korootiAd The auxiliary battery controls the functioning of the inside electronics in the car. Meaning, entertainment, dash, etc. Also, in the S class W221 Mercedes, since the gear selector(P,R,N,D) is a electronic gear selector, if the auxiliary battery fails, it can cause you not to be able to switch gears from the small gear selector that is on the steering wheel column. It depends on the model of the car, but mainly to answer your question, it controls a lot of the electronic stuff in the car. It is the secondary battery in the car. Hope that answers your question.

According to the Mercedes Benz website, On average, auxiliary batteries have a service life of up to seven years, more or less depending on usage and driving conditions.

The auxiliary battery you replaced with, was it from Mercedes Benz dealer or after market? After replacing, have you driven the car for some time? I know sometimes it can take some driving to reset the computer and for it to pick up that it’s been replaced.

@@meetbhuller6324 thank you for your reply. It's an aftermarket battery that had great reviews as far as a replacement for Mercedes. I've put about 400 miles since then.

@@JohnDoe-zg8jm Apologizes for getting back late here. Were you able to get the issue fixed?

Hi, Sorry for the late response here.I totally agree with what you said. I feel like the older Mercedes were built with quality and for lasting. The more the newer ones, its more plastic and the quality on them just keeps going down. I agree the W210 and w2I 11 was made with quality. Thanks for sharing your thoughts!