Mercedes-Benz models are well-known for their impressive technology list, and many of their modern cars have two batteries – the main battery and an auxiliary battery. If this auxiliary battery develops a malfunction, it will show up as an error message on the dashboard. The warning will be generic, but should feature a small battery symbol. AUXILIARY

Usually when voltage converter fails, you will see flashing on-board computer error fault message with the following quote "auxiliary battery malfunction" or "stop vehicle shift to P leave engine running" warning message, which constantly stays on and that creates a big question for mercedes owners - what does it mean ? To find out more keep reading further!

These two trouble codes are the most common for mercedes-benz cars.

You will know that it's the secondary battery that is at fault, because the car will still turn on and some functions will still work. The auxiliary battery does not affect the car’s mechanical functions. If you are unsure, you should be able to diagnose the fault with an OBD fault code reader.

The most important thing is that we now know the issue and what to look for in the car, second thing on the priority list is to find out which auxiliary battery is fitted to your car as you will find out later by reading our blog that there are two different types of batteries.

In addition bear in mind if your car has different language as main language it will show up with different name for example in russian language Резервная АКБ неисправность and so on.

What to Do Next?

In many new Mercedes models, the auxiliary battery is located at the top of the front passenger footwell. You will need to remove some nearby plastic mouldings and peel back the carpet to gain access to the battery area, and the fastenings can be undone with a 10mm socket. You should also disconnect the main battery before attempting the work.

Once the fastenings and the plastic cover are removed, you can take out the voltage converter by taking off a couple of small tabs. The voltage converter is also known as the capacitor, and can be easily sourced. It is a relatively common problem for the current Mercedes C-Class (W205 S205 C205) S-Class (W222),  E-Class (W213 S213 C238) and GLC-Class (X253, C253), amongst other models and A205905341480 capacitor prices vary online.

Then, simply reverse the process of removing it. You will need to re-fasten the two clips and leads that hold the voltage converter in and bolt the square plastic cover back on. Make sure the carpet is fitted as it should be when you reattach any plastic trim pieces you have taken off.

If your car for example is S-class W221 R-class R251 ML W164 GL X164  etc different than listed above, it's battery location will be different and it should be in the trunk (boot) area near fuse box.

For E-class W212 S212 C207 A207 A0009829308 auxiliary battery is located at the driver side on the side panel upper one, to access it you will need to remove plastic protection cover.

Then in this case you just need to unscrew positive and negative terminals  bolts, remove old N000000004039 auxiliary battery from it's original location and put new part back, once fitted auxiliary battery malfunction error code will dissapear automatically, there is no need to visit dealer shop afterwards.

What is an Auxiliary Battery in a Mercedes?

Mercedes-Benz cars have two different type of auxiliary battery also known as mercedes secondary backup battery, it completely depends on the car model, year and many other specifications.

For example E class W211 S211 W212 S212 C207 A207 ML W166 GL X166 C class W204 S204 S class W220 W221 A clas W176 W177 CLA W117 CLS W218 C257 Sprinter W906 Vito W639 W447 B class W246 W247 G class W463 G500 G55 G63 AMG cars have small auxiliary battery located at the luggage compartment (boot, trunk) or under the  front side upper cover at driver side  and it is a copy of normal size battery just "mini" size and few models have this battery fitted under  the driver side upper panel, connected the same way as main battery with positive and negative terminals.

So the first step is to check which battery is used in your mercedes by opening a hood (bonnet) and trunk (boot), in the trunk this part is usually located nearby fuses if after inspecting these two places you weren't able to locate small auxiliary battery it means your car uses voltage converter.

Auxiliary battery is responsible for running and powering additional accessories in the car such as stop go function and many other, once it detects failure none of these functions will work.

For other models for example C class W205 C200 C220 C250 C300 it has also auxiliary battery but it is more like small module ballast also known as voltage converter, but it has the same purpose as other type battery - to run and power up additional accessories on the car.

What is Mercedes-Benz N000000004039 Auxiliary battery ?

N000000004039 A000000004039 12V 1.2Ah lead-acid battery is second model of the auxiliary battery also known as backup battery used for other mercedes cars such as GL X164 GL450 GL550 GL350 GL320 S-class W220 W221 S320 CL-class  W216 CL550 CL600 CL63, R-class W251 R350, ML-class W164 ML250 ML300 ML350 and many other.

This model is completely different to voltage transformer, as it has more similar look to the standard battery compared to other model, genuine part was made in taiwan.

N000000004039 is usually located at the rear of the car in the trunk (boot) area, near fuse box.

What is A0009829308 auxiliary battery ?

One more type of the battery for mercedes cars are A0009829308, it is very similiar looking for the previous model described above, but it has little bit different shape and different location for positive and negative terminals.

A0009829308 battery has few comaptible mercedes-benz oem part numbers A0019822708, A0009829608, A0049820008 and all of them are exchangable and compatible with each other.

As you can see there are many different OEM part numbers for mercedes-benz backup batteries A0009827008 A000 982 70 08 and so on.

Can you re-charge N000000004039 auxiliary battery?

Genuine Mercedes-Benz auxiliary battery N000000004039 12V 1.2Ah is rechargeable as it uses lead-acid materials for the ub1213 battery, but ofcourse as every single car part it has life time and time by time it might completely die or you might use all it's power due to left music inside the car or too much usage of accessories and not enough driving for longer distances.

How much does it Cost to Replace Mercedes Auxiliary Battery?

The average cost for a Mercedes-Benz auxiliary battery replacement is between 200-300 USD. Labor costs are estimated between 50-100 USD, all of these prices are estimated and may vary. To save a lot of money xenons4u is offering auxiliary battery replacement part at our store and step by step guide to replace this battery, so labour charge will be saved as well.

If this does not completely fix the problem, you may wish to take your car to a Mercedes service center or replace the whole auxiliary battery. Like the main battery, it may fail repeatedly if it has lost charge.

Where is auxiliary battery located ?

As you did understand from our blog there is usually three different locations for auxiliary battery and all depends on the car model.

The main three locations are: trunk (boot) near fuse box, at passenger side under footwell light or driver side under upper side panel.

How to Replace Auxiliary Battery on Mercedes Benz?

For some owners of Mercedes it might an issue and big question mark, meanwhile experts in DIY might replace it without any hassle.

We always recommend to use professional garage or fitter to do that job, but if you have decided to save money and do it yourself you can always follow our guide, which includes step by step explanation how to replace auxiliary batter. Once replaced there is no need to visit dealer shop it will fix auxiliary battery malfunction instantly.

This guide could be found here:

Mercedes-Benz auxiliary battery function

Once you see on-board computer DTC fault it instantly pops a question in your head, can I keep using a car? Is it save to drive and so on.

The main function of mercedes-benz auxiliary battery is to provide voltage to "stop start" function, so this function may not work until you solve battery malfunction.

You can keep driving a car for while, but it is always recommended to fix any fault as soon as possible.

What does a Mercedes auxiliary battery do?

There are 2 types of auxiliary battery for Mercedes-Benz cars. Some cars have mini battery, very similar to primary (main) battery just much more smaller in size and other models auxiliary battery is completely different. This new shape battery aka voltage converter has been fitted to new C class W205 S205 C205 E Class W213 S213 GLC X253 C253 and S W222 class cars.

New shape auxiliary battery is completely different if you compare them to the first generation auxiliary battery and it has second name  for it - voltage converter or convertor.

The auxiliary battery runs some or the most of the'cars additional functions or accessories such as PDC sensors, multimedia, various radars, stop start function and so on.

Like every other electronic module or part it has life-time and eventually it will wear out and fail at some point.

Is it safe to drive with auxiliary battery malfunction?

The answer is yes and no, it is always not good to drive with any kind of malfunction on your vehicle as you don't know how it will affect car's performance or other functions.

Based on our knowledge and experience when new generation voltage converter also known as auxiliary battery fails, it is safe to drive for 100 miles for sure or even more, meaning that this part is mostly responsible for additional accessory functions such as "stop/start" and other accesories which aren't important whilist driving,  so you can definitely drive your merc.

Voltage Converter part numbers and compatibility

Mercedes-Benz part has few different OE numbers, which are below,  additionally for our blog readers we have collected a list of compatible cars as well.

Auxiliary battery voltage convert has 3 part number, the newest one is A2059053414, which supersedes older numbers A2054400073 and A2059052809.

The most common Mercedes-Benz warning messages for faulty A2059053414 auxiliary battery:

  • Auxiliary Battery Malfunction
  • Backup-batteri Fejl
  • Batterie de reserve defaut
  • Bateria auxiliar falha

The most popular diagnostic trouble code DTC for faulty converter:

  • B21DC01 - The buffer battery of the electronic ignition lock has a malfunction. There is a general electrical fault
  • B21DC01 The buffer battery of the electronic ignition switch (EIS/EZS) is faulty. A general electrical fault exists

Hella Voltage Stabilizer oem number:

  • 8ES011590-701

Mercedes-Benz voltage converter part numbers:

  • A205 905 34 14
  • A2059053414
  • 205-905-34-14-80
  • A205 905 34 14 80
  • A205905341480
  • MA2059053414

Voltage converter part number A2059053414 supersedes:

  • A205 440 00 73
  • A2054400073
  • 205-440-00-73
  • A205 905 28 09
  • A2059052809
  • 205-905-28-09

Auxiliary battery part numbers:

  • A0009829308
  • 000-982-96-08
  • A0009829608
  • 001-982-27-08
  • A0019822708
  • 001-982-27-08-28
  • 004-982-00-08
  • A0049820008
  • N000000004039
  • A0009829208

Compatible Mercedes-Benz cars:

  • C Cass W205 Saloon Sedan
  • C Class S205 Estate Touring
  • C Class A205 Cabriolet Convertible
  • C Class C205 Coupe
  • C Class 2014 2015 2016 2017 2018
  • C Class C180 C200 C220 BlueTec C250 C300 C350 c350e Hybrid C400 C450 C43 C450 C63 AMG
  • CLC W257 2017 2018 2019
  • E ClasS W213 Sedan
  • E Class S213 Estate
  • E Class C238 Coupe
  • E Class A238 Convertible
  • E Class 2016 2017 2018 2019
  • E Class W212 S212 A207 C207
  • E Class E200 E250 E300 E350e Hybrid E400 E450 E200d E220d E300d E350d E400d 4MATIC E43 E63 AMG BlueTEC
  • ML-class W164 ML250 ML300 ML350
  • GLE W166
  • R Class W251 R350
  • GL X164 GL450 GL550 GL350 GL320
  • GLA-class X156 GLA180 GLA200 GLA250 GLA45 AMG GLA220 CDI
  • GLC X253 C253 W253 Hatchback Coupe 2015 2016 2017 2018 2019
  • GLC GLC300 GLC350e GLC220d GLC 220d GLC250d GLC350d GLC300 GLC43 AMG
  • S Class W220 W221 S320
  • CL-class  W216 CL550 CL600 CL63
  • S Class W222 Sedan 2013 2014 2015 2016 2017 2018
  • S Class C217 Coupe 2013 2014 2015 2016 2017 2018
  • S Class A217 Convertible Cabriolet 2013 2014 2015 2016 2017 2018
  • S Class S300 BlueTec S320 S350 S400 Hybrid S500 S550 S65 S63 AMG 4Matic

What Battery Should you Choose?

auxiliary battery malfunction

For more information about a Mercedes-Benz auxiliary battery malfunction, contact Xenons4U today! Our team of experts are on hand to answer any questions and help you find the right capacitor for your Mercedes. xenon lemputes