Auxiliary Battery Malfunction: Mercedes E Class W212 Replace

[@carbuying]

✅ Bosch Automotive S6590B Lead Acid Battery AGM Type: amzn.to/2u837hY ✅ Mercedes-Benz Genuine OEM Auxiliary Battery: amzn.to/374ey9k ✅ Klein Tools MM400 Multimeter, Auto Ranging Digital Electrical Tester: amzn.to/2NC3dWi ✅ DEWALT DWMT41019 173PC Mechanics Tool Set: amzn.to/2QZVNxT ✅ DEWALT DEWALT DWST11556 Express Folding Workbench: amzn.to/2qsaRdi

[@garyt123]

Do you think any Motorcycle YTX14-BS lead-acid battery would suffice? You could potentially up the Ah (to last longer) and would probably be cheaper too.

[@santesandroperruzza6183]

where can i buy the replacement battery?

[@davidhall2785]

Thanks for your very informative video on proper way to replace the auxiliary battery in a Mercedes E-350. Following your instructions made the change less stressful than I anticipated. 5 stars!!

[@amhandweiser43]

Good video, but please invert the order of disconnecting/connecting the poles. Always disconnect first the ground (negative) pole first, then the positive (and avoid it contacting any metal part, for your main battery remains connected). Reconnect poles starting with the positive.

[@carbuying]

you got it

[@markvincent4521]

The Owners Manual says the disconnect other way (p.348).

[@pyroretired]

Came here to say this...I was cringing as that metal wrench was moving around on the postive terminal... for example from owner's manual for the starter battery on 2014 E250. page 359 "you first remove the negative terminal clamp and then the positive terminal clamp..." You otherwise could zap yourself pretty good and create some sparks if the wrench touches the frame as you complete the circuit... granted the the battery in the trunk is pretty small...you can still damage some sensitive stuff.

[@matteroffact6997]

I am trying to understand why disconnect the main battery before replacing auxilary battery..im trying to learn my husband has no idea😮

[@railroad6601]

This is the same battery (14-BS) as in the 2015 Mercedes GL450. Good video with good information and very detailed.

[@dantethewiseone4372]

Learned something new today.... Great job ... straight outta Kenya 🇰🇪🇰🇪🇰🇪🇰🇪

[@911Mitul]

Had the same error on my E220 CDI today, your video was brilliant thanks for the advice.

[@carbuying]

Glad it helped thanks for watching Mitul

[@rauldiaz8035]

I had the same problem, in E220cdi but when i change auxiliar y batterie tthe system eco dont change yelow from Green. Can I do?

[@911Mitul]

@Raul Diaz Go for a long drive constant say 30mins at a highway. Don't have air-conditioning on. The alternator will kick in then the stop start will work. Check your eco switch is on. The yellow light needs some juice before it kicks in and goes Green at a constant drive.

[@rauldiaz8035]

I Drive in Highway to 120km/h and air conditionee off during 30 min but eco dont change to Green

[@frankmartinez6888]

Thank You! First you helped me with my key fob... and now this! Your step by step guide is awesome! Thank you!

[@frankmartinez6888]

FYI - the Bosch Battery you have listed from Amazon is a perfect match and fit. Just changed it out this morning.. even has the side vapor plug thing...

[@carbuying]

You're welcome!

[@amurray7224]

Would love to watch that key video having issues with mine now also.

[@TruCrimeQueen]

@@carbuying I just ordered the MB battery in your description for my 2014 E350. That is the correct one, right?

[@wildavis1010]

Just got gifted a E30 MBZ. Thanks for the informative video.

[@davidclarke2822]

just changed my battery in '14 E 550-works great thanks for help!!

[@fxpthl]

Just wanted to thank you for this great video! I did this replacement using it and it was a "slam dunk" ! The replacement battery was purchased at an AutoZone store and included the extra hardware required to complete the install easily. The did charge me a refundable feel for the "core charge" but got it back when I turned in the old battery. Once again, thanks for your help and the savings of Big $ if it had be done by a dealer!!!!

[@carbuying]

Glad it helped congratulations on fixing it yourself Edward!

[@fxpthl]

carbuyingtipscom yes i deed and saved Big Bucks from what the MB service folks wanted!!!!!

[@jocallis8244]

Edward was model did you have?

[@lannamonday2847]

Thanks for doing this video! It was exactly what I needed to replace my own battery. :)

[@TruCrimeQueen]

Did you order the Mercedes’ battery in the description?

[@hanifamenen1082]

you said you'd mention whether it's absolutely necessary to change this battery when such a warning message comes up. Is it? Could you tell me why too - whether yes or no. Thank-you. Good video!

[@busigqasana5958]

Hallo Sir My car Mercedes Benz Model CLA 200 year 2016 is showing me the same prob of Auxillary Battery Malfunction. Plesse tell me where is it in the car??? Your videos are really appreciated

[@cedricspencer3208]

Does changing the Battery in E350 2011 affect electrical components in anyway, also how many cold cranks should I look for when purchasing a battery for this car ?

[@carbuying]

It's always a good idea to provide backup power when changing the battery. As far as CCA, you need to look that up in your manual.

[@MrMarcuscostello]

Thanks for he video. Any thoughts on why my stop start would not work again after replacing the battery?

[@carbuying]

You mean the car's start stop button to turn on the car? That should not be connected to the auxiliary battery

[@MrMarcuscostello]

@@carbuying yes you are right. I should have said the ECO function. It doesn't kick in anymore.

[@holikoff]

@@MrMarcuscostello I had the same issue back in summer where the stop/start function stopped working and ECO would not turn on. I got the main battery checked at autozone and was told the battery went bad so I replaced it. After 1 or 2 days the ECO and start/stop started kicking in! So go get your main battery checked. Now though I’m getting the “auxiliary battery malfunction” error message and the “stop/star” stopped working again including the “hold” function where you hard press the brakes to hold the car at traffic lights. So Initially I thought “stop/start” is fully dependent on the main battery, but it looks like not. ECO and start/stop rely on both batteries to be fully functioning!?

[@garyt123]

@@MrMarcuscostello @Shukhrat is right. You should look to your main battery. The charging circuit is routed from the alternator to the main battery and then to the auxiliary battery. There is a voltage regulator between the two to prevent the aux. battery draining the main battery and potentially preventing starting. If the auxiliary battery is faulty you get the auxiliary battery malfunction error, if the ECO function stays yellow and rarely, or never, goes green (with no Aux. Battery warning) then its your main battery or a combination of the two.

[@joe_notjo5103]

Thanks for the video, saved me a trip to the dealership 👍🏻

[@carbuying]

Glad it helped Joe!

[@kidjoe8254]

The question guys if the exility battery malfunction pops up later on if you do not replace it will it kill the battery of your vehicle the one you keep in the front engine will it cause it to die? Any fee back would be grate

[@carbuying]

The 2 batteries are likely isolated. Your car still starts ok with the auxiliary battery message, so this means the aux battery is not negatively affecting the main battery.

[@kidjoe8254]

@@carbuying thanks I needed a new battery

[@ulvenkommer151]

Thanks, great info 👍 Now I know why the start/stop function became irregular some time ago. Just recentely the display info appeared. Got a 2014 C207.

[@carbuying]

Glad it helped

[@gkendric]

I will check but would love to see a troubleshooting video involving the attached battery relay as it can also fail and would love to see steps to test whether it's the battery or the relay and describe the function of this relay. I have this error message and when the error is displayed a check of the voltage from each relay terminal to battery negative yields that there is a voltage difference. I suspect the battery is not holding the charge anymore when the error is present but I'm wondering how to determine if it's a bad battery relay.

[@frenberg]

Hey I have the same problem I think. Testing the aux battery is giving 13.0V so I assume it’s probably something else ... likely the relay or something else. Would be sweet to not have to buy everything and do the old trial and error approach :/

[@carbuying]

So it sounds like the system is not seeing the voltage. this is one of those cases where you really need the service manual to show wiring diagrams to see all inputs to the ECM, or to know what else it looks at to determine the voltage is low, because it should not read low voltage when the battery is at 12V or above. So maybe it's the relay, maybe something else in the chain.

[@gkendric]

@@frenberg In my case it was the auxiliary battery and I replaced it with one that was actually made in the USA from Battery's Plus, a Duracell and that corrected the problem. A test of the battery revealed that the battery was defective and needed replaced, an easy fix.

[@lisawalker7132]

Thanks so much, because I panic 😱 this morning!!!…. Thanks again… I feel like I can do it myself…. Smiles

[@posterlion]

Remove negative cable first. Always! Why does no one know this?

[@carbuying]

For those of us who are careful, it's a moto point does not matter which one you undo first. I you remove the ground cable first, what it you accidentally drop your wrench and it shorts the positive post of the battery to the ground? Same short circuit problem.

[@AustinTXProgrammer]

​@@carbuying Procedures exist so that careful is less important. Eventually we will all make a mistake. If the wrench is on the positive terminal it is going to spark if it touches anything metal. If it's on the negative terminal, the only danger point is the positive terminal. Once the negative terminal is disconnected, this changes, and then the only dangerous point will be the negative terminal.

[@TheGalifrey]

@@AustinTXProgrammer Exactly! It's not a moot point when your dealing with the amount of stored energy in one of those, even worse when your dealing with a truck/bus battery or 29kwh of RV battery!

[@garyt123]

Always the negative first. No argument. You used to be able to do this either way, on vehicles with no ECU (so basically most anything before 1989/1990), and no harm would be done (except maybe a few pretty sparks). Since then auto-electrics has become auto-electronics and this is a whole different ball game. Not only does removing the Negative terminal first reduce the posibility of shorting but also prevents the voltage in various large capacitors inside the myriad of onboard computers from doing nasty things to memory circuits and CPU's via all those NPN type transistors and other circuits. That E350 Mercedes has 9 (yes, nine!) computer control modules in the transmission alone, assuming its not the 4x4 version (which I think has two or three additional modules). Each door has 2 OBC's (Onboard Computers), so that's 8 in the doors. When you start looking at ECU's, Airbags, Audio, Auxilary systems, Starting & Charging, etc. you quickly discover 40-50 OBC's and ECU's all around the car. All those ECU's and other onboard computers are designed around Low Side Switching, this means they are ground referenced and the entire design is layed out in such a way that the only way to guarantee not damaging/corrupting anything is by 'switching' (ie. removing) on the Negative terminal first, and reconnecting Negative last. This is NO joke and is NOT optional; unless of course you really want to shell out a couple of hundred dollars, and up to several thousand dollars, on replacing one or multiple failed ECU's or other OBC's. Sure you could get lucky, but why take the risk?

[@garyt123]

@@carbuying Totally wrong I'm afraid. Thanks for the great video BTW, there is way to little regarding auxiliary batteries, so thanks for taking the time! (Just that one error though)

[@glover19677]

Very helpful thank you very much

[@terrencecarlin3766]

Great video! I have a 2013 GLK 350 4Matic. My message went away but the ECO is still not functioning. What next? Someone suggested changing the Aux battery relay....

[@carbuying]

Not sure, sometimes we have heard it can take a day for the problem to correct itself. Maybe wait a few days before going to replace any relays

[@alexgonzalez866]

I had the same thing happened when my aux battery went out and when replace eco still didn't work everything else did. Just replace main battery and eco work again maybe that will help

[@TheGalifrey]

Thanks for the video, am replacing this exact battery at the weekend!

[@carbuying]

Good luck!

[@kevinquezada4029]

i have a e350 as well, but my car doesnt hold when im at a stop?

[@iamjshep3]

I have a 2014 E350 and same. Whoever had the car built didn’t equip it with that feature is all.

[@irq001]

I have a 2013 E400 Hybrid . Does the process to replace the aux battery remains the same , this model being the W212 too ?

[@scricinel77]

Auxiliary battery only seens to last around a year before needing to be changed. Is there a voltage regulator somewhere? E350 CDI BLUEEFFICIENCY

[@samuelrahimic7929]

Would the auxiliary battery some how affect the fuel gauge? My aux battery light came on and after a little while my gas guage is showing its empty

[@cyrealsekatane8834]

Very informative 👏

[@carbuying]

Thanks Glad you liked it

[@Zera1171]

No need to disconnect the main battery before replacing aux battery? Thanks

[@carbuying]

No need to disconnect the main battery.

[@Zera1171]

carbuyingtipscom replaced it myself, thanks for the helpful video!

[@cencereechols7716]

Where did you get the battery kit?

[@augieschultz2530]

Thanks for the help.

[@thresiapilate8334]

I replaced the auxiliary battery and still will not start. Please give me a recommendation or suggestions. Thank you 🙏🏾

[@carbuying]

Are you talking about the car not starting? The auxiliary battery has nothing to do with the car starting it is the main battery that deals with the car starting.

[@ronke2084]

How long can you drive with the auxiliary battery malfunction warning?

[@carbuying]

We drove 2 weeks with it.

[@machinetradereurope7853]

iS THIS THE SAME type for the 2012 model also?

[@chasewang6483]

I’m having the same problem with my 2016 e350 now I’m going to change it myself. Thank you so much! I think I need to change my main battery too, is it basically the same process? And is there any computer codes?

[@carbuying]

No computer codes to change, when you change the auxiliary battery, the problem goes away on its own. Have you completed your repair and was it successful?

[@mrjehad84]

Hello, thank you for your video, I had the same error ( Auxiliary battery malfunction ) on my E220 CDI, It happened for few days and then it disappeared by itself.. Do you think the battery has recharged itself ? or the error will come back again and I need to replace it ? Thanks

[@carbuying]

Likely you are starting to see the tip of the iceberg. I hope it does not come back, but you can expect it to.

[@halimhoussaini4224]

هو بمثابة إنذار وربما سيعود من جديد واذا رجع هنا وجب عليك استبدال البطارية

[@reyetom1]

I changed the battery for a new one but the warning still showing up. What can I do ? Thanks for your help!!

[@carbuying]

It should go away on its own right away. Check to make sure the battery voltage is over 12V. Your model might need to have the error message reset using your OBDII port.

[@Dic3.20]

hello, I also know an E class from 2014, with a 2.0 petrol+CNG engine, the same message appeared on the dashboard, do you know where that 12 volt battery is?

[@topformautosales2103]

Will the auxiliary battery malfunction prompt cause the check engine light to pop up?

[@carbuying]

In this video at 0:14 you can see the main check engine light is off, but the Auxiliary Battery warning is in the display. We don't know for sure if it will turn on the check engine light in other cars.

[@mewiththeface6717]

Duracell 12v 14ah battery has the same exact measurements with 20 more cranking amps. It would work too

[@carbuying]

most likely yes

[@bianbian428]

Thank you so much!!! I'm doing this tomorrow.

[@carbuying]

Let us know how it works out for you? Do you have ECO mode also?

[@MyGoose24]

My faux battery just came on will.this stop the car

[@snarestud940]

On my 2014 E350 luxury, I no longer have the eco-symbol on the dashboard. But the light still turns green on the instrument panel in the center. Do you know what the problem is?

[@carbuying]

It might still be your auxiliary battery. If that battery voltage drops too low or it does not hold a charge, then it won't turn on the ECO mode.

[@snarestud940]

@@carbuying the brake hold still works though. Is that normal?

[@jeffreyjames2812]

Hello. My 2014 mb e350 screen doesn't work. Radio works just fine. Any help? Thanks

[@carbuying]

Did you ever get your screen issue resolved? Usually holding down the center button for 10 seconds will reset it and bring it back to life.

[@FranciscoMartinez-bu4hc]

How many auxiliary batteries does a 2014 ML350 have? I replaced the one I found by the spare tire with a Duracell (dura12-1.3f) 12V. I also checked the main battery area under the passenger seat but there wasn’t one their. I’m still getting the same message of aux battery malfunction. Do the Duracell batteries come uncharged?

[@carbuying]

We are not sure on this model. Try the MBForums find your model car on the forum and ask you question there. We find lots of answers there all the time, there is always someone who knows the answer.

[@yingviolin3742]

Hi, there! Thanks for the video! I want to make sure that the Mercedes benz battery from Amazon you posted is the right one for 2014 E 350. It looks like it is for w211 instead of w212. It is non-returnable so I want to check with you before I order the Mercedes one from Amazon. Thank you!

[@carbuying]

Don't check with us, check with amazon.

[@drenghala]

I have the same question and Amazon reviewers say it doesn’t fit 2014 E350, could you please post the correct link to buy it? Thank you

[@yingviolin3742]

@@drenghala I actually ordered it from Amazon and it is a different kind so it doesn’t work. It was also very hard to return it so don’t order it from the link. I went to MB dealer and got the right one in one second.

[@drenghala]

@@yingviolin3742 Thank you so much.

[@jeffostroff]

@@yingviolin3742 What was different about this battery that it did not work? I used the automatic model check on the landing page on amazon for both the Bosch and Mercedes Battery. If the voltage is the same, and the size of the battery case is close, then it should fit. What about this battery caused it to not work on your 2014 E350? I saw others asking on amazon if this battery fit the 2014 E350 and the answer was yes. Virtually any battery with similar contacts and screw holes on top of the contacts should work. I installed one from Autozone in my 2014 E350 and it worked. Also there is the link to the Bosch battery as well

[@jhonatanmiranda5289]

Do i need to replace it? Or it should be fine?

[@carbuying]

Yes if the system tells you the battery is bad, you should replace it, provided the issue is not with one of the other components.

[@jasonb4196]

Curious to whether or not the main battery needs to be disconnected while doing the swap on the Aux Battery? Also my Eco light for my stop start is completely gone off the dash. Yes I have stop start I have the build sheet for my car from the dealership using my Vin# also have the button beside the parking sensor button yes the light goes green or off when I hit the button just the light on the button nothing on the dash as stated above. I'm hoping my Aux Battery will make my start stop active again. I also just bought a brand new Optima Yellow Top today.

[@railroad6601]

I changed my aux battery, no need to touch the main battery.

[@pdthfc]

I have replaced my battery over a week ago and done in excess of 200 miles but the eco light hasn't changed colour and no box around it as it was before any ideas?

[@yoshita4653]

Good explanation. But I have a problem when shifting gear to reverse for automatic transmission. It doesn't activate sometimes. If someone can help, please.

[@carbuying]

Not sure that is affected by the auxiliary battery

[@deth5619]

There is a reset process for the transmission in the w212 mercedes. Have you tried that?

[@khadijahjackson2394]

I have the same issue. How do you do the transmission reset?

[@RDSZ]

My e350 warning light came on,at 25k ,the dealer replaced it under warranty a now at 32k the light came back on. I wonder if the dealer batteries are garbage. Thanks for video.

[@carbuying]

You aux battery should have a warranty, does it? We have put about 7,000 mile son this car since the battery change for the aux battery, and so far so good.

[@donparadise3157]

Interstate Battery carries these batteries and will even replace

[@deriklongokailer]

Nice video!

[@rauldiaz8035]

I had the same problem in E 220Cdi but the system eco dont change from yelow to Green. What can I do ?

[@EireFirst2024]

Heya if you wouldn't mind, I'd like to ask your advice on something please - I have a 2014 e class & the stop start is not working, no warning signs at all & doing the battery test on the dash is saying I have 14.4 volts when running, I hope that gives you enough information to maybe have a stab at an answer... Thanks in advance 👍

[@d.a.f.5982]

figured it out yet? maybe replace main batt too.

[@EireFirst2024]

@@d.a.f.5982 ye it was the main battery.

[@ETPAK]

can anyone tells me where is this battery in 07 S550. It is not behind left dash fuse box.

[@carbuying]

Did you check the trunk?

[@ETPAK]

@@carbuying no i found it. It is behind left front wheel fander cover. Real crazy...

[@jamesreilly1431]

Have ML320 SUV Main battery and Auxilliary under front passenger seat. Pain to replace

[@carbuying]

Mercedes can't make up their mind where to put these batteries

[@gtonagtona]

hello, after replacing auxiliary and main battery of my glk 220, the message of malfunction remain. can i replace the system or i need star diagnosys? thanks

[@carbuying]

Give it a day or so, when we changed ours, the problem went away over night, or driving a few miles to get the battery back up to charge. You can also try clearing code, and hopefully it does not come back up, and hopefully you did not buy a faulty auxiliary battery

[@gtonagtona]

@@carbuying thanks,i think that i have ti go in mb service.

[@gtonagtona]

@@carbuying hello,mb service has replaced the auxiliary battery because are default. thank you

[@junbarz361]

Where's the auxiliary battery on 2014 SL550 located at?

[@carbuying]

Don't know on this one, try the Mercedes MBWorld.org Forums

[@jimbaldinger479]

Perfect! Exactly the info I need. Thanks!!

[@carbuying]

Glad it was helpful!

[@jonathanwilkinson242]

hey! does the auxiliary battery help start the car?

[@carbuying]

No, only the main battery starts the car

[@jonbrown2514]

Can this battery not just be taken off and charged?

[@PK-kw1zu]

Does this require coding for the bluetec cars with start stop?

[@carbuying]

No this should clear the check engine light on its own

[@tomburke4652]

They don't call this 212 Engine. That's the chassis w212. 2013 and up Engine 276 and older ones called 272. Same body style.

[@carbuying]

No one ever refers to their Mercedes by the engine even the forums the categories are subdivided by W204, W212, W213, etc.

[@marklutes]

@@carbuying You're both saying the same thing. He's just pointing out that at 1:57 in the video you say "...otherwise known as the W212 engine". Slip of the tongue, I'm sure. Good video - thanks for posting it. Very timely for me!

[@streetmaster2006]

Thanks man!

[@fitimfitim4914]

Hey man great video. What’s the name of the exact battery please, can’t seem to Find it on eBay in the UK. Could it be called something else?

[@carbuying]

Don't know we picked it up at Autozone they looked it up and found one that would work.

[@IrfaanThian]

followed exactly for my gla200 but still has the error msg . 😢

[@PASSNAGER61]

Can someone tell me where can I find the auxiliary battery on my 2011E350 Mercedes

[@Auron380]

I just replaced my auxiliary battery last week. It lasted exactly a week before failing again. Is there any advice you might have for this?

[@carbuying]

Maybe you got a bum battery, or maybe it wa snot connected tight enough and so not charging.

[@aymanawwad3168]

Hello, I just replaced the auxiliary batter form E350 but still getting the message of low auxiliary battery ? Should I reset the computer and how ? 2006 Mercedes E350

[@carbuying]

I would recheck the voltage of the auxiliary battery with the engine on. Also it can sometimes take a day or 2 for the message to go away. Do you still have the problem?

[@aymanawwad3168]

carbuyingtipscom thank you for reply, i just did that and got 14.1V but am still getting the same low battery

[@jeffostroff]

@@aymanawwad3168 Have you tested your ECO function and does it work? Did you test the brake hold function as shown starting at 1:10 in this video? If those are working it could mean your engine fault code needs to be reset using an OBDII reader, although with most cars this message should clear as soon as everything is working.

[@mikeangel1934]

Can These Batteries Be Charged? Like How You Would A Normal One

[@carbuying]

They should be getting charged while in place and the engine is on

[@EpicStays]

@@carbuying I also am wondering if it can be charged. I have a 2017 E400 and the car is less than 25k miles. So I'm thinking the battery just lost charge. It was at Mercedes being repaired (up to 3 weeks) so I suspect it spent a lot of time just sitting there. In addition, I don't travel much due to working from home and sometimes the car sits for a couple days at a time without being started or driven anywhere. So with all this being said, once I received the car back from the dealer and the car sat for a couple days after, I got in it again and I'm getting that malfunction code. I also did drive it around in that state for some time and it went away and and my eco/hold functions worked. But then again after a couple days of not being driven, it returned. I'm hoping I can just charge it back up?? What do you think?

[@baltasaar]

@@EpicStays just drive the car for a couple of hours to charge the battery….

[@EpicStays]

@@baltasaar that's what ended up happening. It's tough bc I don't need to actually drive much anywhere.. but there were a couple of days that week after I posted my comment where I had to drive 30 min each way and I think that did the trick.

[@baltasaar]

@@EpicStays yea, try to everyday accelerate the car, i mean floor it, when u go faster, the alternator go faster, sooo the battery will get charged

[@mariedemiranda938]

Where is it located in a cla-250 2014 this is a great channel

[@carbuying]

In your car it is likely underneath the right hand side dashboard there is a panel that you unscrew and drop down and the battery is located in the left side of that panel undercover

[@sigonyelanandipha1997]

Im stressed because my C200 shows that i don't know who can help with it ordering it may be east but who ?

[@Jordanalani]

Where i find this type of battery in Sweden if i dont want to buy the original one from mercedes? I have an E220 CDI from 2014

[@stevewasilow5556]

Thanks for the info. I just picked up a 2011 E350 with 125k miles. I’ve had it a week and just got the aux bat msg. I’ve always heard the older MB were money pits, but couldn’t resist once I test drove. How many miles on yours? Have you had good experience?

[@BionicRusty]

I owned an ‘08, E350 Coupe, BlueEfficiency and it was probably the best car I’ve ever owned. It had about 90k miles when I sold it. Certainly not a money pit. Yes, it had some wear and tear/maintenance done to it but it was so good that I’ve just bought an E220d Estate AMG Sport Night Edition as my ‘retirement car’. I hope you’re enjoying yours.

[@justwondering1967]

@josephstalin7223 yeah me too, I am wondering the same thing now.

[@m4sta2k]

I have the same car, is it possible to connect subwoofer amplifier (150w) to this battery or do I have to do it trough the main one in the front? I guess they are connected together or? Anybody? Thanks

[@carbuying]

I would recommend connecting to the main battery.. Don't connect something as complex as audio transients and subwoofer amp power draws off this tiny battery. You don't want this type of transient voltage on a battery where sensitive electronic systems are powered from.

[@cprflorida]

My aux battery display came on after the car sat for a few months and needed the main battery to be charged. Does this really mean that the aux battery needs replacement since the error happened after the need to recharge main battery

[@carbuying]

Unknown. The condition triggers when the car thinks the aux battery is not holding proper voltage

[@alexalox741]

How can I know which is bad in my car????? 2010 w212 E350

[@nyblanco]

I purchased a replacement battery for my 2016 e400 model myself from the dealership and my ECO works once in a blue moon out of nowhere... why??

[@carbuying]

Your auxiliary battery might be going bad, check that battery out too.

[@kaanyakit7761]

Hi . I have 2014 E class and having the same warning recently but I noticed that my Eco button sometimes comes on and than goes off againg. Also intelegent light system stops working againg its on and off. Is this normal when you have " Auxiliary Battery Multifunction " on display? Thanks

[@carbuying]

yes, it means the aux battery is ready to go.

[@renatopesce4435]

Io ho una mercedes cls 350 x218 2013 shotinbrak dove si trova la batteria??

[@cprflorida]

Perhaps, I can also attach the battery chargiing kit to the aux battery and hope that it also is charged, since the main battery is connected thruough the alternator, and by running down the main batterry, it ran down the aux battery, since that battery was replaced 2 years ago.

[@cprflorida]

well I tried to charge at 2 amps over night and still with aux battery malfunction. I don't think it is bad, because it still shows tire pressure and other things. So how do I get rid of the error light,

[@carbuying]

The error light goes away on its own when you install a new battery. It probably still senses somethng wrong with the aux battery

[@MegaAlbeagle]

How about I changed the auxiliary battery and after 1 month message came back and doesn’t go away the faulty message even though in changed it

[@joeduffy3309]

the battery needs to be coded

[@MegaFiremech]

just a word of caution to everyone always always remove the negative cable first and reconnect it last

[@splabber7846]

Yes, this is the first rule of working on a vehicle battery. Rule 2 is to use an insulated tool wherever possible.

[@mptrader1620]

So true. I come across so many videos where the positive is removed first. Just do not get it.

[@oscgigi0808]

I have the same problem and Mercedes saying that I have to reprogram The battery so the Eco feature can work again with Is that true or they just want to charge extra money?

[@carbuying]

No you should not have to reprogram anything. Ours worked when we changed the battery. Might take a day for the error to disappear

[@tigerali7]

Anyone knows where is the Auxiliary battery location on 2017 E 300. Thank you!

[@joshmyers2212]

The auxiliary battery isn’t in certain models, it’s an old message from previous years models. Double check but this is the case for my e220d 2016 👍

[@carbuying]

We were sure we had one on the 2013 C250 and after 2 hours of searching realized there was not one. If you can't find it and on the forums search for it, then there may not be one.

[@megant.bearce575]

Where is the auxiliary battery in the 2014 350E Wagon

[@carbuying]

Don't know, you'll have to go looking for it, try the trunk first like we showed, then try under the front passenger seat, then under back passenger seat, then in the left side of the dashboard like we showed. Mercedes puts them everywhere and anywhere.

[@emmanuelocran52]

I have changed my own but still appear on the dashboard saying auxiliary battery malfunction, I checked the battery it’s ok too what will the problem

[@2000markar]

same issue with mine. changed still getting error message

[@emmanuelocran52]

@@2000markar so what did you do?

[@marcwoodruff2571]

I took mine out and it read 12.7 volts, 79%. I had this replaced at the dealership in 04/2018 and getting the Auxillary Malfunction message? Should I replace it?

[@carbuying]

Sometimes they can read good voltage but have issues. You can have Autozone check the battery for you with their machine that runs it though tests and tells you if you need a new battery.

[@cprflorida]

So if it came on as a result of running the engine battery dead, how do you get rid of the light indicating malfunction when it is not malfunctioning as my eco works, hold break works and air pressure works. So how do I get rid of the light

[@carbuying]

Chances are the battery is about to go, the ECO mode might still work, but I bet in a few weeks it might not work

[@teoweeli]

what does the aux battery do ?

[@carbuying]

among other things in red light eco mode, the gas motor shuts off, so this battery keeps the electronics alive.

[@karlozzperez8499]

I can not find the auxiliary battery of a mercedes benz model E 350 year 2010, can you help me locate it please

[@carbuying]

Autozone should be able to cross reference a battery for you, unless you want to go to the Mercedes dealer and pay $250.

[@jamesabarza6559]

thank you, excelente video

[@carbuying]

Glad you liked it!

[@mkhan8902]

I have a 2016 GLA250. The automatic start/stop function caused my car to shut down twice this week. So when I came to a stop, engine shuts off automatically, and when it tries to turn back on it can’t and my screen went black & put the car in neutral. No message came up! I think the auxiliary battery needs to be changed. Any input anyone??!

[@erikandrehoglund55]

I cant charge this battery right ? Just buy i new one right?

[@carbuying]

The battery charges on it's own when the car runs. If it no longer charges there is nothing you can do for it.

[@stephencooke2011]

is there an auxiliary battery in a 2010 E350 and where is it

[@carbuying]

don't know, check with your dealer

[@KimboDogg07]

@5:41 you disconnected the battery terminals incorrectly, you did it backwards. Always disconnect the negative then the positive, then when you reconnect it goes positive the negative... Then you put the positive connector In a static conducive plastic bag... Hmm.. Safety first but everything done here is wrong...

[@carbuying]

Since you're going to be an alarmist, at least think of it from both sides. So you unfasten the ground cable first. What happens when you make a mistake with your wrench and short the positive terminal of the battery to an expose metal part that is connected to ground?

[@Qlii256]

@@carbuying Nothing happens that could break the car, that's why @KimboDogg07 is explaining you should disconnect the negative first. The other way (as shown in the video), you would short out the battery when touching a metal part of the car.

[@leszekmajewski4132]

Where is Auxilinary Battery in Mercedes CSL550 2010?

[@carbuying]

Not sure, try the Mercedes Benz forums, someone there will know

[@johnbates606]

I’m pretty sure it is in a horrible place check drivers side behind centre console. Under a cover

[@donruth1073]

Should I disconnect the main battery before working on the auxiliary battery?

[@derrickphillip9887]

Where is battery for 2004 Mercedes CLK 500

[@carbuying]

Should be in the trunk. If not, try dashboard on left side of drivers side dash, through side access panel.