donpb

I have noticed when I press the auto-fan button, the a/c always comes on also. What's up with that? I mean if it is the dead of night cold, I would kind of like to be the one to choose if I need the a/c on instead of it automatically coming on by default. Is there a way to change that feature? And if the a/c button is on, and it is colder than the a/c setting, then does the compressor even bother to kick in? Or am I just worrying about nothing and should just leave the a/c button alone even though it turns on with the auto-fan button? Thanks.

healthservices

ac does not just chill the air, it also dehumidifies. Have you ever notice when you hit the front defroster it also turns on the ac?

And if you wonder what dehumidification does, it removes water from the air meaning the windows will not be foggy anymore.

DavidF

When you press "Auto" the system does just what it needs to do to condition the air and cabin automatically, like said before, the a/c dehumidifies the air to prevent fogging. BMW suggests a/c is always on, summer or winter, so the auto function is doing just that.

In the winter, the heater is reheating the conditioned air.

Allen

I think a lot of us don't like the A/C compressor be ON all the time because on the older cars, the compressor could be a pretty big drain on the engine...thus reducing gas mileage. And of course, putting wear & tear on the compressor...which was/is an expensive part. In the "old" days, when I needed cold air, I would turn ON the A/C...but most other times it stayed OFF...either way...it was MY choice, and I had control over it..which I liked.

With todays cars...a couple of points: 1 - I don't think the A/C compresor has nearly the drain on the engine that the old cars did...thus, the gas mileage isn't affected nearly as much. 2- Even though the A/C is ON...I don't think that necessarily means the compressor is actually running. For example, when you first start the car, I think the compressor is OFF, even thought the A/C light is ON...in the "old" days, I would always be SURE the A/C was OFF before starting car, because I didn't want the drain of the compressor present while the battery was trying to turn over the engine. Another example, when the outside environment is perfect (good temp, low humudity, etc.), I think the compressor is OFF..even though the light is ON. If the temperature or humidity rises enough...the compressor turns ON. I could be wrong about that, but I THINK that is correct.

luigi524td

Although the A/C light is on in the "auto" mode, the A/C compressor cycles ONLY [regardless of temperature] when sensors instruct it to do so to perform functions in addition to cooling inside or outside air. And, if I'm not mistaken, that may actually extend the life of the A/C compressor.

DavidF

Running the a/c compressor year round is a good idea to prevent seals from drying out (due to long periods of inactivity in the winter months). Of course, you can always turn off the compressor and leave the rest of the system in "auto" mode.

healthservices

With the benefits, why would anyone want to turn off the ac when it is cold? We are not in the 60s anymore.

AJH

The little green Air con fair strikes again.....Damn that fairy!

donpb

@luigi524td
I believe you hit the nail on the head.

I do appreciate the other comments also because I learned a bit more about the system.

I usually am trying to warm the interior of the car at the times when the a/c appears to be on when I pressed Auto. And I was thinking, ok why does the stupid thing turn on the a/c when I am obviously trying to warm the car? And that then leads me to turn it off manually. And yes I am using 60's mentality in 2011. In the olden days, both used to be on at the same time and you had to turn off one or the other. And also the gas mileage would go to caca with the a/c on. I probably get fooled thinking the compressor is engaged because when it is cold, I am experiencing the initial blast of cold air which immediately has me assume the a/c just turned on full blast. Ugh.