Mark O

My 2021 GLB has about 6000 km on it. So far it is a very nice ride. yesterday the fan start making a deep pitched, annoying noise, almost as if the fan blade was hitting something.

Anyone else experience anything like that?

W205C43PFL

Hmmm, are you able to record the noise by any chance for us to listen to?

pjw1967

Longshot. On a long trip with my grandson in the pass seat, I noticed him close the far right a/c vent to stop the flow of air onto him. With the road noise on concrete at highway speeds I didn't hear any difference. A few days later I had a WTF moment. What's all the noise? My first thought was a faulty a/c motor. I had that previously on my '13 Durango. My one remaining memory cell popped up and said check that all the wheels were open. Guess which one was still closed.

Mark O

Thanks for that suggestion as didn't check on that. if it persists, I will try and record a clip.

Mark

Vladimir Livson

Yesterday I had that issue. I started the car and I heard rattling sound coming from the center vents, just like you said as if fan blades were brushing against something. Drove to the store, and when I came out and started the car the sound was gone.
My best guess is that something got into the intake duct (leaf or an acorn) and when I turned the engine off, that something fell to the bottom of the fan housing and stopped interfering with the fan impeller.

Mark O

Well I did check the vent openings just in case. Have tried to make a point of keeping leaves cleared out from under the hood and wiper area so if it turns out to be something like that, then there is a design issue that renders this a non rural use vehicle. I will give it a couple of days to see if the deep rumble goes away. It is quite objectionable when the fan is operating at the higher speed settings so it can reman this way.

Thanks for the tips .

Vladimir Livson

Which design issue are you referring to?

Mark O

I was just suggesting that if a vehicle can't sit outside without the risk of ingesting something like a leaf into the inner workings then that would be a design shortcoming from my perspective.
I am not certain that the problem I am experiencing is caused by that scenario. If it is, the problem is apt to resolve itself in fairly short order. If such is not the case, I'll take the car back to the dealer for attention.

Kbell92

This just started happening to me yesterday. Loud fan noise.. I haven’t been able to find a how to video or diagram to go in and see if there are leaves/junk in the blower motor. Have you??

Vladimir Livson

Based on the diagram the fan blower is behind glove compartment, but I would just take it to the dealer. I did clean a ton of leaves and etc. around intake this morning. The cabin filter is rather easy to get to, it's at the left side of passenger foot rest area all the way at the end where carpet meets the glove compartment area.

Vladimir Livson

A quick update.
Got in the car last night, it was about 90 degrees inside, from baking on the sun all day. AC was on "Auto" and fan kicked in on high speed and it was very loud (like sitting inside the propeller plane). I drove through the summer and it was never that loud. I played around a bit and noticed that "Auto" mode has only 5 fan speed setting, however "Manual" has 7. Once you manually increase fan speed passed 5 the propeller plane takes over, go back to 5 and it's quite again.
So I wonder if there was an Over the Air software update where they changed how fast the blower fan runs?
I will also check my cabin filter this weekend, to see if there are any debris against it. If air filter is clogged it would make the fan try to run faster to push the air through.

Vladimir Livson

So I pulled a cabin filter this morning. There were some oak tree pollen pods in there. Cleaned the filter, ran the fan on highest speed without filter to see if anything comes out, put the filter back and rumbling noise is still there on fan speed settings 6 and 7. Gets quite again when you drop down to 5.
At this point I will have to deal with it when I go to the dealer in December, when my Service A is due. The temperatures should be moderate until than so I do not have to listen to the loud fan.
P.S. I sprayed engine compartment with peppermint just in case this is a chipmunk related issue.

Mark O

So I will post an update after my service visit later this week

190Efan

I would suggest that you post your question in the GLB section of this forum for additional help which you can find by scrolling down the main forum page. The forum section you've posted your question in is the GLA section which is a different vehicle from the GLB that you own.

Mark O

Sorry. I thought I was posting in the GLB forum.
In any case, my GLB went to the dealer today to see if they could resolve the issue. Sure enough, a leaf had found its way into the ventilation system.

The dealership was wonderful about addressing the matter but clearly, or at least clearly in my opinion, there is a design flaw in the air intake for the cabin ventilation system. I have two vehicles at the same property and have had so for three decades. I have acquired new vehicles every few years while living at the same location with the same vegetative cover and never had this issue with any other make or model. I am disappointed in this level of technical planning by the design folks but am looking at a DIY solution that does not include indoor storage. If no solution is forthcoming, then I will have to go back to a previous manufacturer for a product.

Vladimir Livson

Mark:

Thank you for providing an update. I would think a simple pre-filter would have prevented this issue. Aquarium pump pre-filter or Activated Carbon Filter fabric, which is black in color, very porous and sturdy (plenty sold on Amazon). Next time I am at the dealership I will ask them to take a look at the cabin blower.

Thanks.

Vladimir Livson

I can confirm what Mark O stated back in October. I had my service A done this week at the dealer and asked them to check a loud cabin fan noise. They took the blower out and found leaves in it, causing the fan to be out of balance. Cleaned it and put it back at no charge, works fine now. Mark was right that it is a design flaw. Looking at their parts diagram the cabin filter is after the blower, therefore nothing is stopping the leaves and debris to be sucked into the fan.
I am thinking of installing window screen mesh over the air intake openings to prevent leaves from getting inside the vents.

smooth1234

i have the exact same problem what did you find out was the issue

Vladimir Livson

There were leafs and acorns inside the blower.
Dealer removed the fan, cleaned it and put it back. Issue resolved.

ninjutzu

It is clearly a design problem. I complained and they told me that the filter is after the fan. I had the same problem, car is under tree as were all the other cars before. No problem with any other cars, GLB immediately started to make very strange noise when using the fan. It seems that all is about leafs that reach the fan.
Wondering if there is any "aftermarket" fix for this ridiculously stupid design flaw, clearly unexpected from a Mercedes.

Vladimir Livson

I glued black window screen mesh over the air intakes, and had no issues since.

ninjutzu

Oh, what a great idea! Thank you!
I will give it try once there is a bit of summer here as now they promised some snow next week so for sure no leaves yet :-)

Vladimir Livson

There are also 3 smaller intakes at the bottom of the plastic plenum, so don't miss those, as most of the debris collect there.