M-Class (W166) Produced 2012-2015

HVAC fan speeds

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Old Feb 25, 2019 | 11:40 PM
  #1  
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HVAC fan speeds

Anyone else feel that the fan blower isn't up to par?

I literally have to have it on 4-5+ setting to get any decent air flow. 1-3 barely does anything, and in summer the A/C needs to be near maxed to get some good cooling.
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Old Feb 26, 2019 | 12:59 AM
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i only seem to feel weak air blowing from the driver and passenger side door window vents, even when on max defrost the air blows like crazy on the front windshield, but those small side defrost vents barely have any air coming out of them. even had 1 time after a gym workout where my side windows were not able to unfog even though i had max defrost running the whole time.

thats the only time i felt the fan blower wasnt up to par.
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Old Feb 26, 2019 | 08:53 PM
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I don't think the dash vents do much when the heater is on (making some assumptions based on your canada locations)... I have no issues with mine down here in SoCal all summer long, I usually leave it at 68 deg. Temps are great, air flow is great and I like the air blowing right on me.
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Old Feb 27, 2019 | 01:23 AM
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my dash vents work fine ( the ones you can tilt and angle and also open/close a bit with the wheel/knob). they blow nice and hard when i set the air to blow on those vents. The vent i was talking about is the smaller non adjustable vent that is a defrost vent for the door window. circled in red in the photo below. that's the only one i find weak no matter what setting i use.
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Old Feb 27, 2019 | 09:55 AM
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Originally Posted by Babukb2
my dash vents work fine ( the ones you can tilt and angle and also open/close a bit with the wheel/knob). they blow nice and hard when i set the air to blow on those vents. The vent i was talking about is the smaller non adjustable vent that is a defrost vent for the door window. circled in red in the photo below. that's the only one i find weak no matter what setting i use.
those should have zero air flow unless you're on front defroster mode and HIGH. What happens when you put it on that?
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Old Feb 27, 2019 | 04:45 PM
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OK, checked mine out this morning and as noted above, they only really worked when I put the defroster on. The flow was modest compared to the dash vents.
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Old Feb 27, 2019 | 05:05 PM
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Originally Posted by KiwiJack
OK, checked mine out this morning and as noted above, they only really worked when I put the defroster on. The flow was modest compared to the dash vents.
then it is functioning as it should. No different on most cars
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Old Feb 28, 2019 | 12:03 AM
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same here, they have always functioned when running on defrost, just as mentioned very modestly/lightly blowing.

guess that's how it is supposed to be for those vents :/
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Old Feb 28, 2019 | 12:05 AM
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Originally Posted by Babukb2
same here, they have always functioned when running on defrost, just as mentioned very modestly/lightly blowing.

guess that's how it is supposed to be for those vents :/
again, this is normal operational for most cars. Why would you want side vents pointed directionally at the windows to be blowing for any other reason than as defroster vents? I'm struggling to find the reason for this thread.... 😂
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Old Feb 28, 2019 | 12:12 AM
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the issue (for me at least) isn't with the fact that they only blow on defrost. I totally understand that the only purpose you would want air at the window is for defrosting, the issue is with the weakness of the air flow from that vent when you are running it for defrosting purposes. I believe the whole purpose of this thread was for the OP to inquire about the weakness of air flow. i just made a comment that air flow only feels weak from those vents. Other than that I am happy with the fan speed/power.
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Old Mar 1, 2019 | 05:11 PM
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Originally Posted by Babukb2
the issue (for me at least) isn't with the fact that they only blow on defrost. I totally understand that the only purpose you would want air at the window is for defrosting, the issue is with the weakness of the air flow from that vent when you are running it for defrosting purposes. I believe the whole purpose of this thread was for the OP to inquire about the weakness of air flow. i just made a comment that air flow only feels weak from those vents. Other than that I am happy with the fan speed/power.
Yes, I was referring to the "weakness" of air flow. There's no issue with defrost, vents, or the temperature of the air during any season. It's just the fan speeds, like I said, you can't really hear or feel anything until about the 4-5 setting which seems odd.
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Old Mar 2, 2019 | 09:46 AM
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The purpose of the small circled vent is to keep the side door glass clear, so the side mirror is visible. It is not intended to directly heat the cabin, although this may be a collateral effect.
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Old Mar 2, 2019 | 10:39 AM
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Originally Posted by GQsmooth
Yes, I was referring to the "weakness" of air flow. There's no issue with defrost, vents, or the temperature of the air during any season. It's just the fan speeds, like I said, you can't really hear or feel anything until about the 4-5 setting which seems odd.
I don't really want to hear or feel anything once the cabin is cooled down. Lower speeds keep the temp and humidity correct without being annoying. More than adequate cooling even here in south Florida.
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Old Mar 2, 2019 | 11:38 AM
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Mercedes differs from other vehicles in this area. Examples:

- engine temp gage when in the normal operating range appears "hotter than it should be", i.e.g the indicator needle gives the appearance of higher than nominal engine temp.
- cabin temperature dial in the vertical position is 72 degrees, which compared with other vehicles is a bit on the warm side for the "nominal" dial position
- HVAC blower settings need to be "higher" (e.g. 4-5 setting) to achieve "noticeable" air flow. Other vehicles have "noticeably higher" airflow at "lower" fan settings.
- fuel gage uses 180 degrees of level indication, many other vehicles (e.g. VW) use a larger angle of sweep for fuel level indication.

It's a difference between vehicles in the UI (user interface). Vehicle manufacturers define "nominal" or "standard" or "typical" setpoints differently. Very subjective and neither right, nor wrong.

Last edited by chassis; Mar 2, 2019 at 10:36 PM.
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Old Mar 2, 2019 | 07:57 PM
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Originally Posted by Kartergreg
I don't really want to hear or feel anything once the cabin is cooled down. Lower speeds keep the temp and humidity correct without being annoying. More than adequate cooling even here in south Florida.
You realize to maintain the temperature at which the climate control is set at, it will inevitably make noise based on a variety of environmental variables including outside air temperature, interior cabin temperature. If you want a quiet HVAC system in a car, I don't know what to tell you.
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Old Mar 2, 2019 | 10:03 PM
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Originally Posted by we47b1me
You realize to maintain the temperature at which the climate control is set at, it will inevitably make noise based on a variety of environmental variables including outside air temperature, interior cabin temperature. If you want a quiet HVAC system in a car, I don't know what to tell you.
I think you missed the point. GQsmooth complained that he didn't hear or feel much on settings 1-3. My point is that once the cabin is cooled down you don't need to run the fan so high to keep it cool. Settings 2 or 3 are often fine for maintaining the temp without hearing the roar of the fan, at least that is the way it has been working for me.
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