Battery or alternator
Thread Starter
Newbie
Joined: Feb 2009
Posts: 7
Likes: 3
From: Hahira, Ga
2009 E350
Battery or alternator
I have a 14 E350 with 46000 miles I got the warning for a bad auxiliary battery replaced it however my stop and go is not functioning correctly. I checked my 7 year old battery on the hidden menu and it shows UB 11.7 after starting it and while driving it goes to 14.5 to 14.8 after driving and stopping for a while it drops back down to 11.9 to 11.7. I stopped at advance auto and had them check it the guy I wasn't quite comfortable with tell me it wasn't the battery but the alternator. I have a hard time believing that since everything else I have researched tells me its the battery. I am headed to get a battery now what are your thoughts?????
MBWorld Fanatic!
Joined: Apr 2006
Posts: 4,694
Likes: 1,829
From: Dallas-Ft.Worth,TX
2016 E350 Sport
You need a Main Battery for sure. Seven years on the previous is great, and almost unheard of in these cars.
BTW, ECO Stop/Start works off the main battery, not the AUX. When it's not working in my 2016, that's my clue to recharge the main battery.
BTW, ECO Stop/Start works off the main battery, not the AUX. When it's not working in my 2016, that's my clue to recharge the main battery.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,550
From: MA
2008 E350 4Matic, 2011 E350 4matic
I'm wondering if everything is actually fine. You're going to get lower battery voltage when the temperature is low. Same with the start/stop, takes a while to kick in especially if it's cold. On my 2008, I have the original AGM battery at 13 years and my W212 has the original 10 year old battery. If you don't trust the load test at Advance Auto, you can go to Autozone and get another load test. You could also get the car scanned to see if there are any other MB specific error codes or maybe clear any existing ones.
Thread Starter
Newbie
Joined: Feb 2009
Posts: 7
Likes: 3
From: Hahira, Ga
2009 E350
Just got back I got the battery from AutoZone the AGM H8 the ride seems smoother the battery is now registering 12.4 it is still in the high 14.4-8 while driving. The stop start has not reset yet I turned it off for now I plan to have it serviced at Buckhead if I can there in time. I am headed off to the store again so I will check it out again I do feel much better than earlier. Thank you for the follow-up I will keep you posted.
MBWorld Fanatic!
Joined: May 2012
Posts: 2,359
Likes: 1,555
From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
I'm wondering if everything is actually fine. You're going to get lower battery voltage when the temperature is low. Same with the start/stop, takes a while to kick in especially if it's cold. On my 2008, I have the original AGM battery at 13 years and my W212 has the original 10 year old battery. If you don't trust the load test at Advance Auto, you can go to Autozone and get another load test. You could also get the car scanned to see if there are any other MB specific error codes or maybe clear any existing ones.
Trending Topics
MBWorld Fanatic!
Joined: Jul 2008
Posts: 8,384
Likes: 800
2019 G70 6MT & 2022 Ford Maverick XL
Just got back I got the battery from AutoZone the AGM H8 the ride seems smoother the battery is now registering 12.4 it is still in the high 14.4-8 while driving. The stop start has not reset yet I turned it off for now I plan to have it serviced at Buckhead if I can there in time. I am headed off to the store again so I will check it out again I do feel much better than earlier. Thank you for the follow-up I will keep you posted.
They replaced our main battery a few days after we took delivery due to stop/start not working. So yes, main battery is the culprit.
Don’t worry over the voltages you see. Ours also charges at 14.8 or so. Our Macan’s battery was also just replaced and it at times will charge at 15V. It required registering the new battery and I have yet to see a straight answer as to whether batteries have to be registered to the facelift W212s. But I will say that stop/start worked immediately after our battery was replaced at the dealer. That yours still isn’t working is weird.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Thread Starter
Newbie
Joined: Feb 2009
Posts: 7
Likes: 3
From: Hahira, Ga
2009 E350
I replaced it myself I haven't made it to the Dealership yet I am stationed in South Carolina at the moment just waiting to head that way. Would you know if Tony is still in Services? He was always straight forward and honest with me.
MBWorld Fanatic!
Joined: May 2012
Posts: 2,359
Likes: 1,555
From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
MBWorld Fanatic!
Joined: Jul 2008
Posts: 8,384
Likes: 800
2019 G70 6MT & 2022 Ford Maverick XL
Couldn’t tell you. The salesperson was such an arrogant asshat that we will never go back. Only went back that one time because of the “We Owe” sheet.
