My 05 S80 T6 AC seems always on when the car is running, no matter "Auto", "A/C", "Fan" are on or not.
For example, I have "Auto" off, "A/C" off, "Fan" all the way to zero, there is always some cold/warm air coming out of the vent. I can even use 2 temperature knobs to control the air temperature just like "A/C" is switched on. If I turn the fan speed up, more cold/warm air coming out, but I cannot turn it fully off.
Another thing I noticed is when I am on freeway, speed is high, there seems more cold/warm (cold/warm depends on temperature knob settings) air coming out from the vent.
Any suggestions? What should I check? Thank you.