AUTO or FAN SPEED? Which did you reset and how?

 

I used the switch to the left of AUTO to pull up the Screen showing Airflow, Fan Speed, and Temps
Then moved the Auto Fan speed up to maximum

 

Set the temperature you want, set the A/C toggle on, set the Auto toggle on, and leave it that way permanently, winter or summer. Adjust the blower speed as you want, but leave the other settings alone.

 

Called my service dept. about my weak AC performance. Service advisor said you have to run most cars (including big three) with recirc on. Now I've never owned a car that needed that on anything but the absolute hottest day so that's wrong. The real answer is as @paulmj1 says. You need to turn AC on. Yeah, obvious, but I missed it. On my other cars, the "Auto" setting turns AC on when weather is hot. Manual turn on is only necessary when the temperature is below the setting you give the system. Under those conditions, AC is used to clear humidity as opposed to cooling.

The GLE450 is different. Auto holds a heat setting, but not a cooling setting. You have to toggle AC on, even if the system is set to Auto. That makes no sense to me and the user's manual does not specify this in any clear way. However, I now find the AC works fine and that's good news.

 

What I usually do is keep the Auto and AC on even when its winter. In winter, the AC won't kick in due to the temperature setting, but on summer, it will.
Also, make sure the auto fan speed is set to something higher. When you switch the auto on, there is a separate auto fan speed setting.

 

I have a 2020 450. The AC fan seems louder to me than it should be. I found if I direct the air to the lower leg area and dashboard vents helps reduce the noise. The only problem is by selecting the air directions this way defeats the Auto feature. In Auto, only the dashboard vents will operate.

 

I bet you have one of the dash air vents closed or restricted—make sure you have all the "oreo pucks" under the all the A/C vents in the full open position (should see the white in the center of the pucks). I noticed that when they are partially closed (or fully closed), it restricts the airflow and is loud.

 

 

 

OR.....your dew point sensor could be bad. Yikes...what a pain to fix.

 

Thanks, but all the vents are fully open.

 

2020 gle 450 4 matic, 6,000 miles, no air from any vents, blower operating at max, unit freezes up after 20-3- minutes or so, at dealership for second time, software updates first time, drove car for 45 minutes, same problems. strike 2. this is my fifth mb product. I will not hesitate to pursue lemon law remedies, if dealer can not fix. highly optioned special order car.thanks in advance for any guidance.

 

I also have questions about the AC performance. The temperature of the air is fine and matches my settings, but the amount of air coming out of the vents often seems very low given the super loud fan. The amount of air also seems erratic/unpredictable at times. I've taken it to the dealer a couple of times to address other issues and mentioned AC problems in passing, but each time they say it's working as designed. However, my wife who sometimes sits in the backseat with my newborn also commented that the air flow doesn't seem right, and she knew nothing of my complaints to the dealer.

Tonight I sat in the car and played with various options, and I was able to reliably reproduce at least one problem:

1- Turn off AC in the rear (if you have 4-zone climate), and close the vents on the passenger side, leaving only the 3 vents on the driver side open for maximum effect.
2- Select the AC button so its light is ON, turn AUTO OFF, put fan to level 5 or 6 and in the climate menu, choose only dashboard vents (disable footwell and windshield). So, everything is coming out of the 1 side vent to the left of the steering wheel, and the first 2 center vents to the right of the steering wheel. In this setting, there is a decent amount of air coming out, and at level 7 it actually feels like i'm getting a blast of air on my face (which doesn't happen in pretty much any other combination of settings/vents).
3- In the climate menu, now also enable the footwell vents on the driver's side. Air will flow out of the footwell, as expected. The dashboard vents become much less strong, but I suppose this is to be expected since the total air is shared among more outputs, although a surprisingly small amount of total air is flowing given that all other vents in the car are closed (and rear AC is turned off) and I'm at level 5 or 6 which is almost full speed.
4- Now, disable the dashboard vents from the climate menu, leaving only the footwell vents enabled. This works, and you can hear/feel the dashboard vents turn off (I say 'feel' not only because air stops flowing, but also because it's almost like a vacuum is created).
5- Finally, turn on the dashboard vents again from the climate menu. Result: NOTHING CHANGES! No air at all coming out of the dashboard vents, only from the footwell as in step 4. The fan is very loud and I'm only getting a bit of air through the footwell, nothing else from anywhere else in the car. I wonder where all that fan effort and air is going...
6- Some combination of changing the fan speed or temperature or toggling AUTO on and off will then "unblock" the dashboard vents and get them to start blowing air again, matching the settings that are actually in my climate menu.

So, this is at least one case where the AC isn't working as per the settings in my climate menu, since I have dashboard vents enabled but no air is coming out of them. There are other situations where I felt the AC also wasn't working as expected. Even on Auto mode, sometimes everything seems to work "fine", then after 20 minutes of driving the fan will get quite a bit louder for a couple of minutes, then go back to normal. It just seems like the fan's noise is often not proportional to the amount of air coming out.

Anyway, I'm curious if anyone else can reproduce my problem with the 6 steps above before I take it to the dealer again. I'm on version 080 of MBUX, but I had problems when I was still on FUP2/063.

Another quirk is that if for example I'm not in AUTO mode, and say I have the fan on levels 5 or 6 or 7, then I enable AUTO mode and disable it, the manual fan speed resets to 2 instead of remembering what I had it on previously. I'm not sure if that's functioning as designed though.

 

maalox - I did not go to the lengths you described above, but I do have this issue. The fan runs like mad and only the dash vents are selected and very little air comes out. The only remedy I have found is to use the Auto setting and regulate fan speed by adjusting the temp up/down. I figure at some point, others will complain enough that a fix comes out (thank you!!) - I am tired of chasing things down with the dealer and the Auto workaround is good enough for now...

 

I don't have the exact issues described but I did notice that when footwell and dashboard vents are working simultaneously, most of the air is directed to the footwell. The system is footwell biased for sure.

 

I’ve had a similar issue in the past - fans running on high making a racket and hardly any air coming out.

Made no difference whether it was on auto or I manually selected the dash vents.

It seemed like a vent/flap within the dash that directs airflow was stuck.

Disconnected the battery for a few minutes and it fixed the issue.

 

You most likely have a Faulty thermostat: this is a widespread and possible malfunction that occurs when using an air conditioner. Often the setting is changed to manual rather than automatic, and the fan inside the air conditioner refuses to blow air because the temperature is unknown, or it may also blow warm air.Clogged air filter: the air passes through the front air filters. The chance of this air filter becoming clogged due to dirt, debris, etc., D. is very high and high. And if your air filter is clogged, the air won't vent. If you don't service your air conditioner regularly, this could be a problem; only https://www.marvellous.sg/aircon-chemical-wash/ can help you.

 

This is an old thread but one thing that came to mind and hasn't been mentioned is the condition of the cabin air filter. It the thing is really dirty, i can see the air flow being restricted enough to cause problems.