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Discussion Starter · #1 ·
Every car I've previously owned with automatic climate control has worked similarly to the best of my knowledge. The fan speed would vary according to the difference between the actual and desired temperature in the cabin. My recently acquired 2012 e93 does not adjust the fan speed in the automatic position. I must choose one of five fan settings. For the cabin temperature to stay at my desired setting, apparently the temperature of the delivered air must vary. Is that correct? Isn't that less efficient than varying the fan speed? Just curious.
 

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Nope. Semi-automatic at best.
 

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Not how mine works ( 2006 E90). It adjusts the fan speed as needed. From "2" during lowest demand up to maximum if needed when I get into a hot car. It does get fooled a little on humid days and I have to fiddle with it more in certain conditions than my wife's Nissan Altima, but it also have much more even airflow and overall a more powerful AC system, so I'm not complaining. It could use sunlight sensors.
 

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So I assume that the air delivery temperature varies in order to maintain desired cabin temperature. Is that correct?
I'm not even sure it does that. It will very the fan speed after a period of time but just doesn't seem to be aggressive enough with the control. It takes what seems to be a long time to kick in when the car is hot and then seems like an equally long time to back off as setpoint is neared. For an automatic system, it seems like I spend a lot of time messing with the controls. Throw that little manual thumb wheel into the mix and that's why I refer to it as semi-automatic at best.
 

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Discussion Starter · #8 ·
I'm not even sure it does that. It will very the fan speed after a period of time but just doesn't seem to be aggressive enough with the control. It takes what seems to be a long time to kick in when the car is hot and then seems like an equally long time to back off as setpoint is neared. For an automatic system, it seems like I spend a lot of time messing with the controls. Throw that little manual thumb wheel into the mix and that's why I refer to it as semi-automatic at best.
Oh yeah, I forgot about the red to blue thumb wheel. Semi automatic is correct!
 

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In the E90 LCI version, BMW changed the nature of the A/C program, different from the pre-LCI...
  • in the pre-LCI you selected one of three programs, Auto 1, Auto 2, Auto 3 for levels of intensity (I'm too lazy to use actual names from BMW...this is good enough for conceptual discussion), and the Up/Down controlled fan speed only.
  • in the LCI, you select one of five programs for level of Intensity using the Up/Down button when in Auto mode, and the Up/Down button changes function to Fan Speed only when in Manual mode

BMW provides little to no description of what Intensity does to owners; loosely speaking, Intensity is the control of 'how hard the A/C tries'. BMW provides only a very poor and vague description of Intensity in its technical training to BMW technicians! In a BMW training document, the only thing stated there about 'Intensity' is this...

" Automatic mode - The intensity of the IHKA can be set in the automatic mode
submenu. In other words, the automatic influence of the climate
conditions outside the vehicle on the air volume and
the opening angle of the flaps can be set to one of three different
settings (low, medium, high)."​

Intensity only vaguely relates to fan speed...at Low Intensity it might not ramp up the fan speed much even if the cabin is roasting from sitting parked in hot SW desert conditions, and it only ramps the fan speed higher at Highest Intensity, yet (my guess) only hit Max fan speed if you put the system in 'Max A/C' by pressing that button. (I have been in SW desert in 100-107F degree with my 2011 last year and this year, and only needed to use Intensity 3 (out of 5) normally, except when first getting in a hot parked car and pushing 'Max' button for a few minutes to initially cool down (and letting the hot air rise up and out the moonroof).

Oaker55 said:
For an automatic system, it seems like I spend a lot of time messing with the controls. Throw that little manual thumb wheel into the mix and that's why I refer to it as semi-automatic at best.
I think of it as allowing me to tweak the system for increased comfort, without either altering the desired temperature setting or altering how strong the fan is blowing on you.
Sometimes, in my wife's Toyota, she has to alter both settings...sometimes down to 68 and other times up to 74 and playing with fan speed, yet a 70 degree setting should be comfortable as is. In my E90 I simply move the thumbwheel a bit to the left or right, leaving temp at 69 and not playing with fan speed, maybe bumping Intensity from 2 to 3 or back to 2!
 

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Non, no, it's automatic. The car simply knows what you want better than you do. If it increased the fan speed, you wouldn't be able to hear the engine as well and you'd lose 0.1HP.

I sort of like the thumbwheel so you can decide to put warmer air on your face if you want. The temp adjust in the back is very nice. Most cars you just get a mix of what he front passengers get. Airflow is pretty good back there too...again compared ot most.

Perhaps I'm easily satisfied. I do agree, it could be better. But it appears the engineers are satisfied as from 2006 to 2011, it seems ot operate almost identically.
 
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