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Just changed the voltage converter (205-905-34-14-80) and cabin filter (205-835-01-47) on my 2015 C300. I ordered the parts from Mercedes Benz of Portland for $174.85 total. It took me about an hour to replace them. Now I'm going for a test drive to see if the stop/start is working and if the "shift to park" message is gone.
Last edited by lvbatteryguy; Feb 20, 2019 at 01:20 PM.
Ran a couple of errands after I changed the voltage converter and the "shift to park" message did not appear. But the next day on my way to work, the message appeared and stayed on during my 20 minute drive. The stop/start function still doesn't work and hasn't worked since I bought the car three weeks ago. Anyone have any ideas what I can try next?
I just got the Auxiliary battery malfunction error message on my C400, car was in for service B a week ago.
Since this problem seems to be related to voltage converter, does anyone know if the replacement will be covered under ELW ? I am on ELW, my original warranty ran out couple of months ago.
Thanks
this is a DIY procedure for sure, I just finished changing mine. I have a W205 C300 2015 and the auxiliary battery malfunction message came up about 2 months ago. I was told by the Mercedes benz technician that it was not critical. The repair is covered under warranty, however I'm not able to take it to the dealer so I decided to purchase the spare part online (parts.com) for $104 with shipping included.
I went ahead and did it in about 35 min. the steps are:
1. Remove the cover under the glove compartment, this is a single screw and 2 clips
2. There are 2 cables attached to the cover (bulbs) so you have to disconnect both cables.
3. Pull back the carpet (carefully), it will be hard but the foam behind the carpet can be twisted without any issues
4. there will be a plastic cover with 3 nuts, you have to take them out and remove the plastic cover. You will see the voltage converter right there, which will be attached to the metal piece by a clip and a screw. Carefully remove the nut (Carefully and slowly). and just unplug the converter and replace with the new one and follow the same procedure in reverse.
Be careful with the tools as there are many DC cables under that carpet, so you can easily create a mess if you are not pretty careful.
I did not take any pictures with the details, but it is the same as the one posted earlier here
If you have any questions on this particular one just let me know
Regards
Just wanted to reply and confirm this fix worked for me. Thanks for the post
I just got the Auxiliary battery malfunction error message on my C400, car was in for service B a week ago.
Since this problem seems to be related to voltage converter, does anyone know if the replacement will be covered under ELW ? I am on ELW, my original warranty ran out couple of months ago.
Thanks
For anyone searching this thread I can confirm that the dealership took care of this no charge on a car that was 4 months and 11,000+ miles out of warranty.
For anyone searching this thread I can confirm that the dealership took care of this no charge on a car that was 4 months and 11,000+ miles out of warranty.
Extended warranty won't cover a battery, but the "auxiliary battery" on late-model cars isn't a battery! It's a "voltage converter," which is really a bank of capacitors that store charge like a battery. Since it's part of the electrical system, which is covered, and not a battery, which isn't, it's covered. Good to know and remember for the future. Some dealers might not be as well informed. If your car is older and has a real second battery (either in the trunk or above the driver's feet) you're not so lucky. Either way you get the same message: Auxiliary Battery.
Extended warranty won't cover a battery, but the "auxiliary battery" on late-model cars isn't a battery! It's a "voltage converter," which is really a bank of capacitors that store charge like a battery. Since it's part of the electrical system, which is covered, and not a battery, which isn't, it's covered. Good to know and remember for the future. Some dealers might not be as well informed. If your car is older and has a real second battery (either in the trunk or above the driver's feet) you're not so lucky. Either way you get the same message: Auxiliary Battery.
I don't know anything about extended warranties - never had one - but the dealer fixed this "under warranty" on a car that was more than 4 years old and over 50,000 miles. And if your car is older and has a real second battery you should be reading in a different forum; for the W205, this message means you go to the dealer and get your voltage converter/capacitor replaced, and get a new transponder key battery (or two) while you're there.
I don't know anything about extended warranties - never had one - but the dealer fixed this "under warranty" on a car that was more than 4 years old and over 50,000 miles. And if your car is older and has a real second battery you should be reading in a different forum; for the W205, this message means you go to the dealer and get your voltage converter/capacitor replaced, and get a new transponder key battery (or two) while you're there.
Did they say why they were replacing it under warranty so far after it expired?
Did they say why they were replacing it under warranty so far after it expired?
No, but I told them I was surprised and pleased! They gave me an estimate for needed tires and brakes but I ended up doing those elsewhere for about $300 less. Had a new E-Class loaner too.
I have a C300 2015, and brought it in for recall service in California. It is two months out of the four year warranty, and into the extended preowned warranty. They wanted $700 or so for the repair, 'to replace the battery'. Kind of annoying since this part should be recalled, and it's definitely not a 2:30 hour job.
Please reply here if they actually cover it. They denied me.
Bought the capacitor and did it on my own. It was pretty easy. If you search on YouTube, there is a guy who changes it in real-time and it took him 17 minutes to do it. It took me about 30 mins. 2.3 hours of labor sounds absurd. I’m not a mechanical person by any means and don’t really mess around with cars and I easily did it
Good info that MB will cover it. I’m under extended warranty either way. Nice to know it’s not a battery and on my dime.
Originally Posted by Elbandito
Bought the capacitor and did it on my own. It was pretty easy. If you search on YouTube, there is a guy who changes it in real-time and it took him 17 minutes to do it. It took me about 30 mins. 2.3 hours of labor sounds absurd. I’m not a mechanical person by any means and don’t really mess around with cars and I easily did it
Yea, they are absurd. Where did you source the component capacitor, and did you replace all four to be safe? This actually isn't my car, I'm house sitting for family, and they don't have a multimeter or a soldering gun, but I can probably borrow one. I'd rather do that than wait around for another part. I haven't pulled it out yet, because I wanted to go the easiest route.
Yea, they are absurd. Where did you source the component capacitor, and did you replace all four to be safe? This actually isn't my car, I'm house sitting for family, and they don't have a multimeter or a soldering gun, but I can probably borrow one. I'd rather do that than wait around for another part. I haven't pulled it out yet, because I wanted to go the easiest route.
I searched the part on google, it was an OEM part from one of the OEM part websites.
So you just bought a new part, and didn't replace anything at the component level itself? I have experience with repairing PCBs and such. I can change a bad cap, but I need to know what to order. :-)
So you just bought a new part, and didn't replace anything at the component level itself? I have experience with repairing PCBs and such. I can change a bad cap, but I need to know what to order. :-)
If you do that, you should replace all four. But I wouldn't think it's worth it versus just buying a new assembly.
1. No one has ever specifically called out the "capacitors" as the culprit in the "old" part leading to the "updated replacement part" - just as likely could be the control circuit.
2. If your C-Class was covered under the "campaign" to have the updated module installed - and you and/or previous owners did not have that done - for now that Campaign is still in place
3. Feel free to go ahead and DIY chase this - best way would have someone who is doing - or has done - the replacement/update send you their old/original module - and you can have at it !
I had the fault for about 6 months before I changed it with a remanufactured unit
I disassembled it and found two of the four electrolytic capacitors had burst and the electrolyte had leaked onto the circuit board and some of the components. My intention was to just replace the capacitors and that would have been a very easy fix but the corrosive damage was too much
Moral of the story is that if the message comes up on your screen then act quickly and you may be able to repair the unit at a modest cost.
1. No one has ever specifically called out the "capacitors" as the culprit in the "old" part leading to the "updated replacement part" - just as likely could be the control circuit.
2. If your C-Class was covered under the "campaign" to have the updated module installed - and you and/or previous owners did not have that done - for now that Campaign is still in place
3. Feel free to go ahead and DIY chase this - best way would have someone who is doing - or has done - the replacement/update send you their old/original module - and you can have at it !
There are many reports of leaking caps. Apparently they had a batch of bad ones.
I did the repair today myself. If someone has a schematic of the old and new I'd be interested in deciphering how this design needs a class action dropped on it. I have never repaired a car before. This repair took me 20 minutes to review the video of an awesome guy repairing it, 2 minutes to get to the point of swearing because I dropped the socket wrench extension unfastening it, 1 minute to fish it out, and then about 15 minutes with breaks to make sure I assembled everything correctly again. So from the point of absolutely no knowledge, no ad hoc light attachment, and with crappy tools I did this in less than 45 minutes. 2:30 of labor at the dealership minimum. GTFO Mercedes. My mother would have done this faster than me, but she doesn't have the time to waste on this BS when she returns home.
In return for the awesome knowledge base of this forum and the mechanics who posted the videos, I promise to always support independent repair, and share the knowledge of my expertise for others to use in the future (which I already have done and will continue to do). Really, thanks everyone for sharing your experience on this problem.
I pried open the sh-tbox part, and I could smell the magic smoke all of the way upstairs...The original A 205 440 00 73 design was the villain. I originally planned to refurb the part, but this is not worth it. I paid $84 for a refurb/pull of the newest version.
you are right my car was working perfectly fine despite the auxiliary battery malfunction. I understood it is not an actual battery but a voltage converter. i really dont know what it does. wait to see the MB dealer quote the all in cost for me was little less then 400 usd.
This part conditions the power for the cabin electronics. This is because power fluctuations can damage components.
This part conditions the power for the cabin electronics. This is because power fluctuations can damage components.
I'm not sure why we're answering an ancient question, but as long as we are, let's be accurate. There are no significant power fluctuations at work. The reason Mercedes uses dual batteries is to ensure that the starter battery (the main one under the hood) will have enough charge to start the car if the auxiliary battery has been run down. Originally, the system was developed for the W211 and its Sensotronic brakes, which had an electric pump. Part of getting approval for this brake system was ensuring sufficient voltage even in the event of a serious electrical system malfunction. Mercedes then decided that, with so many electric consumers in modern cars, it was a good idea to reserve one battery for starting and electrical "emergencies" and use another to power most of the car's needs. The system is quite sophisticated and decides when to charge both batteries, when to connect the aux battery to the main electrical system, when to isolate it, when to start disabling high-current but non-essential services (like the rear defroster and seat heaters) and when to start disabling more services in order to preserve charge for the most important uses.
The aux battery has been replaced by a "super-capacitor" bank (confusingly called a voltage converter) in the latest models, but it serves exactly the same function as a lead-acid battery. It's a charge storage device that "looks" like a battery to the rest of the electrical system, but is quite a bit lighter. Theoretically, a super-capacitor should have fewer maintenance issues than a battery but apparently the Korean vendor that Mercedes used had a bad batch of components.
I have similar experience and i am waiting fot the parts from Aliexpress china cost about USD40 with shipping chrage but will take 2-3weeks.
I have driven the car 2 weeks so far and start stop button not working, but car safe to drive.
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