I have been driving around for a while now with the Auto button on and the A/C button off, just for testing purposes (don't ask, just accept it - I wanted to see if it makes any difference in fuel consumption).
I assumed that this would mean that the airflow, blower, etc. would be regulated automatically, but the A/C compressor would stay off.
However, once in a while, the A/C stink will come on pretty strong, i.e., the A/C turns on although the green light on the button is never illuminated.
What am I missing here?

 

I believe AC may be kicking in to reduce humidity.

 

I thought that, too, but its totally random. It happend also on a nice, very cold, dry days, but not when the windows were fogged up (like last week).

 

i found that keeping the ac & auto on always was the best. i have no stink whatsoever anytime in almost 2 years

 

he is right sometime whenI turn off the AC the humidity get quite high so the AC is for keeping the car fresh and cool. Or in HK winter I just trun off the AC and the auto and let the windows down and sunroof open itis so nice.
and you will get about 3hp back for turning off the AC

 

I read somewhere that you'll get better gas mileage with the AC on as compared to driving with the windows/sunroof open.

 

That was on "Myth_Busters" a few months ago. Best gas mileage with windows closed & AC off. Second best; windows closed and AC on. Third; windows open and AC off and forth with windows open and AC on.

 

3 hp more huh pinghuk, and who came up with this number? Where do you get your information from?

 

from Top Gear and 5th gear, thats what they say to get abit more speed in 0-60mph