The GLS is Mercedes’ flagship SUV and many consider it the S-Class of SUVs.
It was first launched as a 2017 model when the GL-Class was renamed after its second-generation facelift.
As can be expected from a top-of-the-line SUV, the GLS offers a supremely comfortable ride, quiet and luxurious interiors, the latest automotive tech, and powerful yet smooth engines.
In this article, we’ll take a look at its most common issues…
Table of Contents
1. Weak Halogen Headlights
A common complaint that a lot of owners have with the first generation GLS is that the standard halogen headlights’ low beams are not bright enough to properly see the road at night.
The halogen headlights came standard on the 2017 to 2019 model years of the GLS, as well as on the older GL models.
The brighter LED headlights were only available as an option in the first gen GLS.
Although halogen headlights have been used in vehicles for several decades with great success, GLS owners report that their standard headlights are not as bright as those found in other vehicles.
Weak halogen headlights are also a common complaint in other Mercedes-Benz models from the same era such as the GLE.
Here is how some owners relayed their frustration:
“The stock halogen bulbs are horrible in the GL/S. MB should be embarrassed to put those in such a nice vehicle.”
“Over time, the low beam lights have faded which make it very difficult to see at night.”
“Headlights are not safe. Forward visibility is very poor. This vehicle should not be driven at night, especially in poor weather conditions.”
The easiest way to improve night-time visibility in the GLS is to replace the stock bulbs with aftermarket halogen bulbs that are much brighter and have a higher color temperature that mimics HID lights.
Swapping out the bulbs is a plug-and-play affair and is also the cheapest option.
Another common fix is to upgrade the bulbs to an HID system or retrofit LED bulbs.
But this requires additional wiring and some modifications to get the right beam pattern since the headlight assembly is not designed for these kinds of bulbs.
Unfortunately, you can’t just swap out the halogen headlights for the optional OEM LED headlights because it requires much more complex rewiring and reprogramming of the car’s electrical system.
If you’re buying a used first generation GLS, it’s best to make sure it has the optional LED headlights to avoid the poor nighttime visibility of the standard halogen lights.
2. Keyless Entry and Key Fob Issues
Many GLS owners have had issues with their car’s keyless entry system at one point or another.
At one point or another, some GLS owners have experienced issues such as:
- Car won’t lock or unlock
- Tailgate won’t open
- Kick-to-open tailgate functionality doesn’t work
- Car won’t start
These strange events can be caused by a malfunctioning key fob which renders the keyless entry system inoperable.
It can be difficult to diagnose since the symptoms are intermittent, and can leave both owners and dealerships baffled.
Here is how some GLS owners described their experience:
“I would say 90% of the time it works flawless for me but the other 10% the doors don’t unlock unless I use the fob.”
“I’ve never had a problem with unlocking upon touch but had major problems with locking, which was very inconsistent. It turns out that the key fob does go “to sleep” after a certain amount of time.”
In a lot of caes, if the keyless system stops working, you can just use the key fob buttons or the Mercedes me app to lock and unlock the car. If the problem persists, you’ll likely need to get a new set of key fobs.
Mercedes-Benz updated their Keyless-Go system sometime in 2019 to prevent car thefts.
After the update, the key fob would go into sleep mode if it was not used for some time.
Older key fobs had difficulty waking back up so the car couldn’t detect that it was in range, which caused many of the issues mentioned above.
People eventually figured out that shaking the keys repeatedly would eventually wake the system up and just did that as a workaround until they could get their replacement key fobs.
It’s also possible that the key fob’s battery simply died and just needs replacing.
3. Odor from HVAC
Some GLS owners have complained about a foul-smelling moldy odor whenever they turn on the AC.
It’s a fairly common issue in 2010-era Mercedes-Benz vehicles which even prompted a class-action lawsuit that the company eventually paid out to settle.
Here is how a few GLS owners described the issue:
“I have put about 6,000 miles on it and a couple of weeks ago I started getting a sweaty gym sock smell coming out the vents at start up. Having never had a car smell this bad.”
“40k miles on our 17′ and summer is in full affect in Nor Cal so the AC is putting in work. I have noticed a not so pleasant aroma when turning the AC on.”
Many GLS owners report that even after replacing the cabin filters and cleaning out the AC system, the strange odor continues to linger.
The moldy smell is indeed caused by mold forming inside the car’s evaporator due to condensation.
Since it’s located just behind the dashboard, the warm, moist and dark environment tends to encourage mold growth.
A lot of GLS owners were able to remove the HVAC’s moldy smell by spraying Lysol, Ozium, or a similar disinfectant solution down the air vents.
If the issue persists, it might be a good idea to deep clean the entire HVAC system which can be pretty labor intensive.
4. Vibration at High Speed
Some models of the GLS suffer from vibrations and pulsations when traveling at speeds over 60 miles per hour.
Vibration issues are more common in GLS models that come with larger wheels.
Here is how a few GLS owners described their experience:
“I just traded my 2017 GLS 450 that I owned for 6 weeks for a new 2019 model. The 2017 had vibration that felt like unbalanced wheels. Now I’m feeling the same vibration in the new vehicle with less than 50 miles on it.”
“After I submitted the vehicle in for the initial service and I had the tires rotated, I noticed that there is a slight vibration/pulsating of the seats, dash and steering wheel.”
High speed vibrations can often be caused by one or a few of the following:
- Poor Wheel alignment
- Faulty wheel bearings
- Worn out suspension
- Wheels are not balanced
- Faulty CV axles
Most of these issues are more common in older vehicles with worn out parts, but some GLS owners have complained that they’ve experienced vibration problems in brand new vehicles.
After performing wheel alignments, suspension checks, and road force balancing, many GLS owners were only able to get rid of the vibration issues after they switched to a different set of tires from another brand.
Several GLS owners who successfully got rid of the high-speed vibrations reported that the issue boils down to the stock low-profile Continental tires that were fitted to the 21-inch wheels.
Aside from switching to a different tire altogether, you can also improve the car’s overall ride quality by switching to smaller wheels so you can use tires with larger sidewalls.
5. Excessive Tire Wear
Another common complaint that many GLS owners have is the car’s appetite for wearing out tires.
A lot of GLS owners have reported that they’ve had to replace their tires at just over 10,000 miles.
While this may be understandable in the AMG models fitted with high-performance summer tires, this kind of tire wear is a bit on the extreme side for the standard models.
Here is how one frustrated GLS owner described their experience:
“I purchased a new 2018 MB GLS550. Took it back for annual service. Told, I needed to replace tires at 13000 miles. Just took it in for second annual maintenance. Again I was told tires needed replacing at 14,000.”
The main reason for the premature wear is the GLS’s suspension geometry. It doesn’t have camber or caster adjustments so the tires tend to wear out quickly at the edges.
On top of that, the car weighs almost 6,000 pounds and they’re equipped with high torque engines that can quickly chew through tires even in normal driving conditions.
To avoid premature tire wear, you have to get your wheels aligned as straight as possible.
These adjustments are outside the factory recommended settings, but they shouldn’t affect the car’s handling as long as you’re not driving at Autobahn speeds.
Switching to higher tread wear tires and getting regular tire rotations can also prolong the life of a set of tires to 30,000 or even 50,000 miles.
6. 48-Volt Battery Issues
The second generation GLS uses a 48-volt mild hybrid system called EQ Boost which has had a few reports of failures.
When there’s an issue with the 48-volt battery, the car won’t start at all since the hybrid battery is also responsible for running the engine’s starter motor.
In a lot of cases, a ‘Stop Vehicle’ error will show up on the dash and will sometimes display either a 48V or 12V battery issue.
Here is how a few owners described their issues:
“We got our GLS 450 about a month ago. 3 weeks and 1300 miles later we got the dreaded red error message regarding the battery. It was towed straight to the dealership. The battery had to be replaced.”
“My car (GLS580) delivered on Aug 6 2021 with 1200 miles on it refused to start today.
I tried to jump start the car and it did not work.”
When the car has a 48-volt battery problem, it will usually end up getting towed to the nearest dealership for a proper diagnosis
Many GLS owners who encountered the 48-volt battery error early on reported that the problem was resolved after cleaning the battery’s terminals.
Apparently, some batteries had their terminals partially painted over which caused electrical issues.
Some dealerships also had to replace a few GLS batteries even though they were fairly low mileage which indicates a manufacturing defect.
Replacing the 48-volt battery should be covered by the warranty, but it can cost around $5,000 once the warranty expires. According to Mercedes-Benz USA’s documentation, the 48-volt battery should have a 7-year/70,000-mile warranty in CARB states.
Source: Car Problem Zoo
Mercedes-Benz GLS Pros and Cons
If you’re considering a Mercedes-Benz GLS as your next car you might be wondering what its strengths and weaknesses are…
- Luxurious and roomy cabin
- Extremely comfy ride
- Cutting edge infotainment and driving aids
- Smooth and powerful engines
- Good handling for a large SUV
- Spacious third-row seats
- Complicated infotainment controls
- Expensive options
- High dealership rates
Mercedes-Benz GLS Reliability Compared to Similar Cars
Consumer Reports ranks the Mercedes-Benz GLS in 7th place with a score of 5/100.
|Make & Model
|Consumer ReportsReliability Score
|Land Rover Range Rover
Source: Consumer Reports
Mercedes-Benz GLS Used Value
We’ve taken a look on Car Gurus to gauge the resale value of a Mercedes-Benz GLS, below are typical asking prices for each model year.
According to Car Edge, a Mercedes-Benz GLS will depreciate 62% after 5 years and have a 5 year resale value of $44,047.
Note: Used model prices will vary depending on trim level.
Source: Car Gurus
What Do Owners Like and Dislike About the Mercedes-Benz GLS?
Based on owner feedback from the Kelley Blue Book site here are what real-life owners love and hate about the Mercedes-Benz GLS.
- Fun to drive
- Driver assist
- Nice family-hauler
- Noisy AC
- Tire wear
“I sold my 2021 GLE to buy this GLS 2022. Much better car, very well equipped compared to the GLE. Smooth ride, comfort and quality. A real S class Mercedes. Maybe the best one I’ve had.”
Source: Kelley Blue Book
“It’s as if your riding in clouds! This vehicle is exceptional I wouldn’t want my babies riding in anything else! We feel so safe in this car.”
“… Very comfortable vehicle, technology is what you would expect for the money. Versatile and roomy. Not disappointed…”
How Reliable Are Mercedes-Benz Cars?
According to a recent report from Consumer Reports, Mercedes-Benz are ranked the 23rd most reliable car manufacturer out of 28 brands, with a score of 34/100.
Source: Consumer Reports