rickth

Hi there,

I'm having a problem with the air conditioning in my 24 GLS 450. When I set the fan speed manually to a high setting (like 6 or 7), it starts blowing at full blast but then keeps going up and down in speed erratically. I understand this behavior in automatic mode, but it's happening even when the fan is set to manual! I also double checked all the 3 zones to see if any one is set to automatic but they are all set to manual mode.

It's especially bothersome when the car is parked in the hot sun. I want to keep the fan on high, but it randomly drops down to speeds like 1 or 2, even though the display still shows it set to 6 or 7. The actual airflow feels more like what you'd get on settings 1 or 2.

I took the car to the dealership, and they saw it happening as well told me this is how it's designed. Their suggestion was to use automatic climate control, but that system switches to manual fan control when you adjust the desired temperature – which defeats the purpose of automatic mode in this situation.. But I don't get why the fan speed would change so much in manual mode.

Can any one with a 24 GLS 450 confirm if this is the same for them too?

mikapen

Can you describe what you mean by "manual fan control?"
I don't think there is one, if you have it on automatic.

There is a fan speed adjustment, but it only sets the basic parameter - A little faster or a little slower than "medium." A graphic shows the relative speed. It's still overridden by the temperature setting, which slows the fan when it approaches your set temperature.
The switch I'm talking about is the one directly to the left of the Auto switch.

When it's set on Auto, The temperature selection controls the fan speed.

A workaround is to set the temperature as low as it can possibly go. I think it will display "Min."

darlop

That doesn't sound normal. But the fan strength can change depending on how many zones are active. Having every zone set to 7 sometimes makes them all work harder. But if you only turn on the front it won't be as strong at 7.

Also it will reduce speed automatically when taking a call or using voice control. But I've never had it change fan speed on its own besides that.

Comprehension is really not your strong point is it.

mikapen

I'll make it shorter for you.
I suggest you familiarize yourself with the cars.

SO, tell me where that manual button is - and explain how it can be primary when you have Auto mode selected.
It doesn't work that way. (Read my post or RTFM.)

Also, if your fan speed doesn't automatically adjust when it approaches the set temperature, or when you get in the car and it's extremely hot / cold when set on Auto, there's something wrong with your car.

darlop

He stated no less than 3 times that he is using manual mode so I don't know what you are babbling on about. He also mentioned speed 6 and 7 which do not exist in Auto mode. Do you even own a Mercedes?

mikapen

Read the first post.
He said the fan speed was changing automatically when it was set to manual.

I think he confused the buttons, but if he didn't, it indicates something is amiss.

Therefore I asked him which button he thought was the manual button. It's a troubleshooting question.

The manual button alters the basic fan speed, and the graphic will show various speeds, but it is overridden when Auto is selected.

New, and new-to-you cars can be complicated, especially if you head down the wrong path with some of the control functions.

Also, what the dealer said, or his interpretation of what the dealer said, was incorrect. Auto does not go into manual mode when you raise or lower the temp setting. (Unless you're not in Auto because you have activated Manual, which overrides the Auto mode.)

There are too many conflicting parts of the story. Needs clarification.

He could very well have a problem, but using the wrong buttons can also replicate his symptoms.

rickth

Hello,

My apologies for the confusion. To clarify, by "manual mode" I mean the climate control is not set to "Auto."

In "Auto" mode, you can still adjust fan speed using the dedicated Fan button left to the "Auto" button. I believe this is what the dealership was referring to.

@mikapen Also, what the dealer said, or his interpretation of what the dealer said, was incorrect. Auto does not go into manual mode when you raise or lower the temp setting. (Unless you're not in Auto because you have activated Manual, which overrides the Auto mode.) - You're right, I misunderstood the automatic climate control. I thought adjusting the fan speed in "Auto" mode would disengage the automatic function and switch to manual control. However, it appears the system allows fan speed adjustment while remaining in "Auto" mode.

However, even on the highest fan speed setting in "Auto," the airflow isn't as strong as setting the fan speed to 7 manually (without "Auto" on). - The core issue I'm experiencing is that the fan speed fluctuates when the climate control is not in "Auto" mode, even though I set a specific fan speed and the dealership is saying that it's by design, which I fail to understand on why would the fan speed change automatically when it's not on Auto?

@darlop That doesn't sound normal. But the fan strength can change depending on how many zones are active. Having every zone set to 7 sometimes makes them all work harder. But if you only turn on the front it won't be as strong at 7.

Also it will reduce speed automatically when taking a call or using voice control. But I've never had it change fan speed on its own besides that. -I understand that the fan speed might reduce momentarily for functions like phone calls. However, the issue I'm experiencing is a continuous, erratic fluctuation throughout normal driving. The display shows a constant speed (like 7), but the airflow noticeably drops and increases like it's switching between settings like 2 and 7 repeatedly.

EWL5

@rickth, can you check your build sheet to see if you have code 913 "Air conditioning preinstallation for hot countries"?

darlop

Yeah like I said that's not normal and unfortunately the dealer gave your their standard reply of "that's how its designed". I guess you could try a different dealer or maybe an independent shop.

The best case scenario is maybe the fan motor is bad and can't keep up. Otherwise if its a software issue then that's something only MB can handle.

rickth

Hello, I just checked. I do not have anything with 913 "Air conditioning preinstallation for hot countries"

rickth

Yes, seems like it. They've already updated the software which didn't fix the issue. I've told them that I don't believe that's it's designed this way and asked them if they can show the new 450 on the lot would do the same, waiting for their response.

jkaetz

Have you checked that none of the climate control zones are still set to Auto fan? If the 2nd row fan is set to auto and the 1st row is set to manual the fan will still change.

You did that. Is it switching between vent mode and recirculation mode?

EWL5

I have it on my MY23 GLS. I can't imagine it would be different on a MY24. Can someone confirm if they have code 913 as part of their MY24 GLS build?

darlop

I've never even heard of that option. Sounds like something for the middle east market.

EWL5

Here it is on my build sheet. I don't live in the Middle East. LOL!

mikapen

So, to answer my own questions about your questions - I spent some time on a hot day and then again on a cold day, trying to replicate your situation.

The following was my Troubleshooting/ verification experience when I entered the car and it was 80°, and it was the same when it was 40:

I hit the Auto button once, which turns off Auto and the red light goes out.

Then I increased the fan speed to seven, with the temp setting at 72F.
The fan blew at that Max speed until it approached 72 - then the temperature at the outlets lowered, but the fan speed stayed the same.

Then I set the temp to 78, The fan stayed the same, temperature got hot.
The reverse: set the temperature really low, The temperature got cold but the fan still blew at 7.

Set the temp setting to 72, (fan still max), waited until It approached 72 and the outlet temperature reduced.
Then I hit Auto (Red light back on) and the fan immediately went to low. AKA normal.

My takeaway:
If all your experiences with erratic fan speeds came while your Auto indicator was off (no red indicator light), there is something wrong.

It looks like I'm verifying your most recent post. I just wanted to clarify what "off" meant to you. That's what it means to me.