Owners Continue To Have Issues With Their Mercedes Hybrids, Dealers Do Not Claim Responsibility

The people at Mercedes-Benz have been making some very interesting choices in late. The decision to axe the V-8 engine from the current AMG C63 couldn't have been an easy one, and while it is nice to have fuel economy an all-electric range, it's even better to have a thundering V-8 that makes you smile. Mercedes is, apparently fixing this “issue” by re-introducing the V-8 to the C-Class, but there is another issue the company seems to have neglected. 

The issue in question concerns Mercedes’ current hybrid models, including SUVs like the GLE and GLS, as well as some AMG and Maybach models, relying on hybrid powertrains. We know that over 116,000 Mercedes hybrid vehicles, produced between 2021 and 2024, were affected by issues with the 48-volt system's ground connection, which apparently, is prone to come loose.

This could, potentially, lead to a fire since the ground connection can overheat. The worst part is, a warning message regarding the 48-volt power supply will be displayed only after the ground connector has already loosened. Mercedes will fix the issue free of charge, but apparently, that's not all. 

A (not so) proud 2023 Mercedes GLC owner and a reader of ours, recently contacted me regarding outstanding issues with his hybrid Mercedes suffering from energy drain, in a very short lifespan. Normally, even early 2000s exotic cars would last about a week if a battery tender is connected. Not here. For the sake of clarity, let's call the owner, Alan. Here's what he said to me: 

“Mercedes feels if you don't drive it over 20 miles a day that you'll have to charge your battery and that you cannot leave it longer than 3 days what the battery will go dead. That's normal according to Mercedes. But yet, they can sit on a daily lot for weeks without the battery going dead. This was put on my repair order in writing after numerous times and numerous parts were replaced by Mercedes factory engineers that stopped by the dealership to investigate”. 

Later, he also added:  

“They actually put in the repair order that I'm not driving enough. This is Hilton Head 20 miles. It is almost 45 minutes to an hour worth of driving”. 

Alan also told me that after just three days, his 2023 Mercedes GLC hybrid would not start. The 2023 and newer Mercedes GLC 300 features a 2.0-liter, turbocharged, inline-four engine with 255 horsepower and 295 pound-feet. The 48-volt mild-hybrid system adds another 23 horsepower and 148 pound-feet, along with an integrated starter generator.  

The two batteries draw power from one another, but when the 12-volt conventional battery (which all cars have) starts losing power, it begins draining the 48-volt system. Apparently, Mercedes replaced numerous parts in efforts to solve the problem, which still persists. Relays, fuse boxes, and more according to the owner.  

“If they didn't think they had a problem they wouldn't have replaced a ton of sensors and switches, as well as two fuse boxes. Now, for them to say you can't let the car sit for more than 3 days without a maintainer that they installed free of charge is ludicrous. I pointed to half a dozen GLCs on their lot. I guess all those batteries are dead”, Alan added during our conversation. 

This isn't an isolated issue as the MB World forum features long discussions regarding the GLC (and other Benzes) having trouble with their hybrid systems. Not to mention the class action suit from a few years ago, due to said issues. According to specialists, the two most common reasons for problems with hybrid powertrains are the Power electronic motor or the high-voltage battery, which typically cause a hybrid car to not start. Alan hasn't given us a detailed list of all that was changed, but he already pointed out quite a few things, including fuse boxes, switches, sensors, and others.  

People sharing their experience with the GLC hybrid in the forums talk about a possible reason being the main controller unit not being grounded, which considering the company's aforementioned service recall seems plausible. At this point in time, Mercedes hasn't really confirmed whether that's what plagues the GLC's hybrid powertrain or something else. 

In any case, the saga with Mercedes hybrid powertrains continues. I will update as more information is available on the topic. If you have any experience with similar issues or if you just want to share your thoughts on the matter, feel free to visit the comment section below.

About the author

Dimitar Angelov's automotive interests made him an expert in a wide variety of vehicles. Japanese brands like Toyota are closest to his heart, although performance cars in general are his favorite segment, which is why he is constantly on the lookout for the best deals on the market. Dimitar Angelov's car passion and knack for the written word led him to complete a Master of Arts in Media and Communications, and classic car restoration. Dim is happy to get behind the wheel of any car and share his impressions. You can follow Dimitar on X, Linked-in, Instagram, and Facebook.