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where is the auxiliary battery in a W166
how to replace the battery.
Tools required ,Screw driver, Torx 40 and 27, 10mm socket,
1. Lift spare tyre cover
2. Remove Torx 27 screw from back panel and lift back panel UP to remove it. Pic 1
3. Remove 2 x Torx 27 screws from trim on right hand side Pic 2
4. Remove luggage holder clip right hand corner Torx 27. Pic 3
5. Remove restraint clip on lower corner Torx 40. Pic 4
6. Pull back panel. Pic 5
7. remove 10mm bolt retaining bracket on the top of the battery pic 6(I used a memory saver in the cigarette lighter fitting in the back, just in case, not sure if it was necessary)
8. disconnect negative terminal
9. disconnect positive terminal (it may still be live so dont earth it) I clipped it behind the plastic cover see pic 7
10. a replacement battery equivalent deka etx14 (cost $199 AU see pic 8) fitted perfectly although i had to bend the terminal fitting to make the terminal fit (see pic 9 and 10)
11. Fitted positive terminal, battery retainer and negative terminal. removed battery memory saver and rebuilt other components. Car tested perfectly.
Last edited by robfolland; 11-18-2017 at 12:52 AM.
Reason: add more information
Thank you for providing this write-up. My 2012 W166 ML350 4Matic w/ Airmatic suspension has a different battery in the same location. Strange that Mercedes uses different batteries. Does the main battery need to be disconnected when replacing the aux battery? ...or with the main battery still connected, can I just disconnect the aux battery and replace it with a new one?
Hi , Yes agreed , using different batterys in different model cars, regardless, i did use a plug in battery in the cigarette lighter port in the back of the car while i was changing the battery, just in case. I did not disconnect the main battery.
Hi , Yes agreed , using different batterys in different model cars, regardless, i did use a plug in battery in the cigarette lighter port in the back of the car while i was changing the battery, just in case. I did not disconnect the main battery.
Sorry, this might be a trivial question, but....can I hook up a Battery Tender to the remote terminal connections under the hood to serve the same purpose as a plug-in battery as I change out the auxiliary battery?
BTW, it was just yesterday that the "Auxiliary Battery Malfunction" warning light came on. The ML had not been driven much over the holidays, and last week, I found that the rear air suspension had collapsed down. It raised back up after starting up the ML, but I had found it in the position again a couple days later. I then hooked it up to a Battery Tender Plus and all seemed okay until yesterday. I had replaced the main battery (under the passenger seat) about two months ago. At that time, I occasionally couldn't shift out of park, or startup would seem just a little weak. A battery test indicated a bad cell.
Hi, When i changed the main battery i did use the jump start terminals as a place to hook up my battery tender at the front of the car. Im not sure if you really need the battery tender to change the auxiliary battery, i just did it as a mater of being sure and was very careful not to earth the battery terminals when changing the auxiliary battery. If your car is not fitted with the cigarette lighter port at the back of the car, i would suggest hooking your tender into the power leads tot he auxiliary battery somewhere just to be sure not to erase any required memory. someone else may have better wisdom than me to say its not required at all.. When i changed the main battery i did use the jump start terminals as a place to hook up my battery tender
Thanks for the suggestions. I replaced the auxiliary battery yesterday. Although I did not get another warning message yesterday before replacing it, I did not get any message after replacing it either. The BatteriesPlus store where I purchased the replacement performed a test on the original auxiliary battery and found that it shows complete voltage, but when you put any load on it, it wipes out. Strange. What else is strange, is that the rear Airmatic suspension was dropped down again this morning. It doesn't seem I have a battery problem, unless there is something wrong with the main battery that I had replaced 2 months ago. Taking it to the dealer to diagnose, as it could be a problem with the Airmatic suspension itself.
Hi, your asking too techy question regarding the air suspension. does sound like there is an issue with air suspension(maybe a slow leak), probably not related to the battery. Nice to hear you had success changing the battery. if you had failed to complete the task correctly I would assume you would have had issues. I would also suggest your main battery will be OK. you can purchase a OBD 11 to check your computer for faults (i did purchase a $210 AU device which lists the faults if there are any, merc i carsoft MB11 Obd2 ). another device i purchased was a battery tester (cost about $20 AU so i dont have to rely on salesmen telling me my battery condition) I will be interested to find out your final solution. good luck.
Thats great news, and thanks for the info, I would have thought a temporary/ tender power source wouldn't be required, but i was being cautious, if you find the reason your suspension is deflating let us all know. very interested.
Thanks for this. Just changed my 8 year old battery. Hope it fixes the intermittent "PRE-SAFE functions limited" errors we've been getting when starting.
I have a 2015 ML350 and needs a new aux battery. Robfolland instructions are spot on and this should be an easy job, but??. I have run into an issue with the new MB battery update. The old battery is part number 019822708 and the new p/n is 0009829608. The new battery is slightly wider and deeper than the old one and will not fit into the bracket. Do I have to modify the bracket or is there a new bracket? Appreciate any help.
2014 E350 also restored: 1969 Camaro convertible SS 1957 Chevy Belair 2dr hardtop
When I changed out both of my batteries the dealer said I had to keep power going to the car while changing. They wanted a fortune to change out the batteries. Anyone that would pay the amount the dealer wanted would have to be crazy. After checking on this forum I disconnected both batteries with no backup and brought the batteries to pep boys. Told them I needed replacements. Paid about 1/3 of what the dealer wanted. Brought new batteries back home and installed them. That was 4 years ago and there was no problem and no data lost when car started up again. I do not know if it is a scam to get more money from the car owners but there was no need for having a back up power source while changing batteries on my car at least. I do not know about other cars but mine did not need the backup.
Hi, i would suggest, just making the battery "fit" either by modifying the old battery holder or making a new one, i presume the replacement battery is the same style of battery (AGM)
2014 E350 also restored: 1969 Camaro convertible SS 1957 Chevy Belair 2dr hardtop
Both went at the same time when the car was about 3 1/2 years old. Have had the pep boys batteries in now a little over 4 years. Took longer to drive to pep boys than to take out and put back in.
Nice work, gee 3.5 years isn't that long, i got 9 years out of the battery in my small Merc . if you haven't disposed of your battery yet, check the fluid level, even though they say its a non maintenance battery, they still use water and dry out quick. a little effort you can get the tops off and top up with distilled water , i found it rejuvenated the battery and lasted several years more
2014 E350 also restored: 1969 Camaro convertible SS 1957 Chevy Belair 2dr hardtop
Turned in core battery is long gone. With the cold weather in northwest Illinois if you get 4 or 5 years on a battery you are doing pretty good. Not that expensive as long as you do not use a dealer.
The change-out is super easy, but the bracket will need to be modified for the new updated battery (part number 9829608). It is 1/16" wider and 1/8" deeper. I used an angle grinder to cut the side of the bracket that faces the outside. This provided enough space and the new battery slid into place. The battery was $145 from the Merc dealer.
I'm about to do this aux battery swap on my truck, I have the smaller 1.2 AH battery. Is there a way to tell the manufacture date on these these batteries? The new one reads 12.7v which is good, but im curious as to when it was manufactured. there is a code: Q006 on the label, any way to decode that?
I'm about to do this aux battery swap on my truck, I have the smaller 1.2 AH battery. Is there a way to tell the manufacture date on these these batteries? The new one reads 12.7v which is good, but im curious as to when it was manufactured. there is a code: Q006 on the label, any way to decode that?
11-16-2017, 07:33 AM
