aweber1nj

Been a hot summer in the Mid-Atlantic. I notice when I have my climate control set to Auto (confirmed by the display and the LED above the switch), the fan speed stays at a moderately-high setting and never auto-adjusts. It's not extremely noticeable on short trips, because typically it's been attempting to cool the interior to my setting (72deg F), but on longer drives you notice that it never changes and the car starts to feel cold (I don't have an independent thermometer to tell you the actual temp).

I've tried a number of things, and the majority (or all) of them take the car out of Auto mode, but anytime I go back to Auto, the same scenario plays-out.

Has anyone else heard of this or experienced it?

I hate taking my car in for stuff like this, because the dealer's shop tends to either just ignore you or not take the time to troubleshoot it (like I said, you wouldn't really notice this if you start the car and sit/drive for just a few mins).

Thanks,
AJ

Daniel6L

Mine does the exact same thing. I just chalked it up to being a poorly implemented Auto A/C system. Sometimes it helps to set it to 75 but I've just been manually adjusting the fan speed which makes the auto system redundant.

aweber1nj

Yeah, when you do that...it's not Auto!

Have you seen any different behavior when increasing the temp to 75? That wouldn't be entirely comfortable to me, but it's an interesting test. I _did_ increase mine to 73 to see if anything would happen....didn't notice any difference.

I also noticed that if I tap down on the Fan Speed it goes to "Auto Airflow", which seems to just be a very low fan speed, but that disables Auto "Mode" and while that can tend to maintain temp for a drive, the next time I get in the car it stays low speed and I have to hit Auto Mode again to cool the car down.

Eagle22

I have a 2019 GLC so it might not be germane to you, but my automatic climate control runs smoothly and auto adjusts as the temperature comes down. I set mine at 74 degrees year round and I'm always comfortable. Best system I've had experience with. Hope this helps.

jj39

My 2020 operates the same as yours in auto. Just think it's a poor design by MB!

Daniel6L

I had the same exact issue and kept raising the temperature setting until the fan speed slowed down, it was either 75 or 76 before it finally slowed down. The ford focus has better automatic a/c.

Takehold

Same here - I turn it to 74 or 75 to slow it down - But for me, the car is still cool to cold at that number so maybe the temperature calibration is off?

wesram

same issue here with the GLC 2020 model. the Auto is poorly designed. In my case, apart from the issue u mentioned, sometimes when i turn on the car the auto is disabled and the fan sound is very high. i tend to leave the temp at 23 or 24 Celsius which avoids these issues most of the time. however, i agree that there is an issue or poor design in this MB. i have an appointment with the dealer on the 2nd of September and this is one of many issues on the list i sent them to investigate.

KCSam

I have the same issue and posted about it several weeks ago. I don't recall anyone really indicating a similar issue. I keep mine at 78 and it STILL gets really cold. I guess I'll need to talk to my local shop about it.

dalazernet

just checked mine. Our temps here were in the low 70s this morning and my fans stayed very low and temperature felt comfortable in the car set for 72.... later on driving home it was in the higher 80s and the fan kicked on a lot higher at first and then slowed down... felt comfortable still set at 72. So, I’m guessing your internal thermostat may either not be calibrated properly or may need to be replaced? I’ve always left my car on auto mode with my old 2008 C-class and the auto in this new 2020 seems to function the same way.

aweber1nj

@dalazernet Yeah, I lease my MBs, so I have gone through maybe 10 or 12 cars. All the previous ones had very good climate control - or at least "predictable" climate control. This car is very different. I never turned AUTO off in my previous cars (maybe to hit Max Defrost or something special).

Does anyone know where the internal temp sensors are? Previous cars you can notice them when you look close at the dash. I didn't see anything at first glance.

Eagle22

Sort of a related question...when running the climate control on "Auto", I have been advised to just shut the car off...and supposedly a fan will kick on to dry out the A/C to prevent mold (and smell) forming in the vents. so far, so good on both my 2015 GLK, and my 2019 GLC. Recently, another person claimed I should turn off the A/C a couple of miles from home to let the system dry out. Any opinions out there. I've searched both owner's manuals for a definitive answer with no success.

aweber1nj

@Eagle22 somewhat off-topic, but I never switched out of Auto in the past, and don't recall ever having an issue with mold/mildew or smells like that. while I don't live particularly close to a body of water, we get a lot of hot & humid days here in NJ, and I guess I have just taken that for granted. If MB told people they had to monitor their trip and remember to turn off the AC "n minutes" before turning off the car, they would probably have a major marketing issue.

dalazernet

Yeah, no problems here with moldy or musty smells in any Mercedes I've owned. I just leave auto on at all times and let it do its thing.

Eagle22

aweber1nj: See...one guy's "sort of related" is another guy's "somewhat off-topic" Thanks for the response...I agree completely. BTW NJ has a great coastline...spent a lot of time offshore of it! (and in Cape May) Hope you're all safe up there!

ParjAS

My 2019 GLC's automatic mode works perfectly. So I'm assuming that this is a 2020 problem?

High Technology

Same issue in my 2020 -- fan runs higher than I would like for longer than I think it should, and it does ultimately get too cold in the car. I typically keep mine at 72 or 73F, and this is the worst MB system I've had (this is my 5th MB with the AUTO system), and definitely worse than any other car with an AUTO system we've owned (probably another 5-10 vehicles). I know it's probably fixable via software update, but MB seems to have a penchant for if it's not severely broken, they probably won't fix it...

JEDC1

I've had my new 2020 GLC for a month and have noticed the same thing. On a side note the good news is that the A/C probably blows colder than any other system I've ever had, which is great considering I'm always hot. The "bad" news is that I'm able to achieve icebox levels of comfort with the temp set in the low to mid seventies (since the auto setting doesn't really work lol). So I basically just shift between auto and manually controlling the system, which isn't the end of the world to me. That being said, I'm curious as to whether anyone has spoken to their service department about it and/or looked into whether there is a technical service bulletin for this issue.

wesram

just to update you guys, i put my car with the dealer couple of days ago and included the note about auto malfunction. he first said nothing is wrong with it, then informed me that they did a refresh on the system. didnt get the car yet but test drove another GLC 2020 with same specs as mine (almost zero mileage), and guess what! same issue and the AC acts crazy. Today since morning it was either freezing us inside the car or refusing to increase the fan speed unless we lower the temps to less than 19 degree Celsius.
judging by the feedback im getting on my other obvious issues on the car, these are all characteristics of the car and will not be fixed. worth to note that the the service manager himself was shocked by most of my comments (to my surprise and good luck, he experience the same issue of Auto switching off on its own when we test drove the car) and agreed that he is less than impressed with the car and promised to send MB Germany all the comments and get formal response from them.

ParjAS

Hope it gets fixed. Guessing you are not in america because you use celsius, the americans on this thread won't be getting much help. Same problems in US also.

Takehold

Has anyone had this resolved? On a hot 88+ degree day the fan stays high and the car gets freezing cold and the only way to get the fan to slow down and get the temp to feel like 72 I have to bump the temp top to 79-80. Not the end of the world and I know I can take it out of Auto, but still, something isn't right. I may take it in this summer just to see if they have a solution.