2018 GLC Auxillary Battery / Voltage Converter Replacement

Replaced an Auxiliary Battery, also known as a Voltage Converter, on a 2018 Mercedes GLC43, with the hope of fixing the auto engine shutoff feature while stopped at a red light.
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[@jimmagnus1200]

I have the same model. If my auto shut off quit working, I would consider it a blessing.

[@simonleung9396]

UPDATED I appreciate you posting the video even though it wasn't the solution to your specific problem. My battery is new and I replaced the voltage converter / aux battery and it did NOT fix the issue. Back to Square 1.

[@edshandymantips4862]

I can’t remember if I mentioned in the video a new main battery fixed the auto stop/start function.

[@bowieskeeter2126]

thank you for this post. i tried to find the battery part number but all i got were the voltage converter. i was going nuts not knowing that the aux battery was also called the voltage converter. thanks again

[@victorlei2526]

Fixed my(Auxiliary battery malfunction ) according to your DIY video. Really appreciate your video which made my DIY project much easier. Thanks!

[@ThomasRSmith-og7zo]

I have the same exact problem with my 2018 GLC 43. Thanks for posting the video. Helped me a lot. Beats taking it to the dealer and paying $400 Dollars for them to install their part.

[@betherealdeal]

Just remember the part he used is not OEM. It’s most likely a Chinamasm You know how that goes! I would buy the part from Mercedes not Amazon. I have the same problem I hope to fix it aoon

[@richardtaylor3762]

Hi, Did you ever get around to doing a strip down on this unit. In the UK the dealer wants $230 to diagnose the problem (it was on the dash), how hard would that be? The part is $231 I never ever enev asked about the cost to fit so all in I guess it would be $550+. I am wondering if I can strip and fix the component. What do I have to loose?

[@isaaclebrun5178]

Is the one from Amazon still working ?

[@edshandymantips4862]

Yes, the Amazon one is still working.

[@durbinmotorworks6253]

Auxiliary battery in this model is used only to put the transmission in park in case of complete power failure (accident).

[@edshandymantips4862]

Good to know - thanks!

[@brianlockyer4389]

After suffering years of these problems i found that a new battery fixes it for a year or so then as the battery deteriorates the stop start starts to fail again. I think it's a deliberate action by MB to stop the wear and tear to their engines and starter motors.

[@edshandymantips4862]

Now that I have some experience the next time the start/stop function does not work due to the battery I’m going to continue to use the battery until it shows other signs of needing replacing. I almost always disable the start/stop function every time I start the car anyway. I believe there was a lot of life left in the battery that I replaced!

[@idigbebop]

@@edshandymantips4862 hello Ed, maybe you discovered this by now, I researched this on my own GLC. The GLC Start/Stop function monitors a few system data points to allow the SS to work. First; main bat voltage, second; cabin A/C set temperature, third; vehicle incline ( steep angle on a hill ) I believe. The data point that led to our car issue was the main battery. The GLC, and many other MB’s, have a constant drain on their main 12v battery. System monitoring, even with vehicle shut off and parked, will draw voltage. The rear electric parking brake is system monitored every 15 minutes for actuation, the keyless entry antennas, rear hatch foot activated lift sys and the security system, Nav and Satellite link are all micro voltage draw on the main battery which will draw down to 50% charge on even a fairly new battery. I have resolved any low voltage issue by simply recharging the battery monthly, or at regular interval when convenient. I invested in a Clore Automotive ( PL2310 ) smart charger. The Clore, a pulse type charger, has the AGM type battery charge cycle select, which the MB uses. I charge both my late year MB vehicles regularly. Easy hookup, set it at 2 amps and let the Clore run it’s programmed recondition pulse cycle. So far so good. Thanks for the video on Aux Batt access. Cheers.

[@paulrowan1501]

Mercedes actually advertises that they beefed up the starter motor, the engine, and electrical circuitry all for the start-stop function. I've rea estimates that this feature saves between one-half and one mile per gallon at the most. What do I care- I'm driving a Mercedes! Imagine if they actually put the investment into something more worthwhile, like say a feature that allowed you to check your oil level on the display, like my 2008 Boxster has.

[@idigbebop]

@@paulrowan1501 It's inconvenient, I turn it off immediately when I start it up. I never measured any increase in mpg.

[@betherealdeal]

@@idigbebop I once saw jay Leno complaining about German cars still using power even after being shutoff. He said it’s hard for Germans to give up power lol I noticed that my feature stopped working in winter time.?perhaps the he main battery is going

[@XxBigBrotherxXX]

Hey quick question. So I swapped out this auxiliary battery. And now I’m getting a message “Auxiliary Battery Malfunction”. Everything seems so I be working fine. But I was wondering if you knew what this could be from? Did I need to do some type of system reset of changing it?

[@edshandymantips4862]

No reset on auxiliary battery, only on main battery. Did you get the message on the old one before the swap?

[@XxBigBrotherxXX]

No I never had that message on the old one. Was just having issues with auto start:stop

[@edshandymantips4862]

@@XxBigBrotherxXX I would put the original one back in and see what happens. Perhaps the old one was good and the new one is bad?

[@betherealdeal]

Did you turn the feature on withe knob thing?

[@edshandymantips4862]

My car has a push button that defaults to on every time the car is started. Once started you push the button to toggle on/off.

[@betherealdeal]

@@edshandymantips4862 😆 ok smarty pants that was funny A newer Benz has a knob you use to setup different settings like turning on the stop And start engine when you come to a stop 😂

[@XxBigBrotherxXX]

You never showed the location of the actual Auxiliary batter. just this voltage converter. I dont believe they are the same thing. The auxiliary battery looks like a tiny small version of the main battery.

[@edshandymantips4862]

The GLC only has the voltage converter. No additional “auxiliary” battery. People use the term “auxiliary battery” instead of “voltage converter”. The voltage converter has capacitors that store energy like a battery.

[@simonleung9396]

they ARE the same thing!!!