Something wrong with cabin Climate control
 

My 2008 X5 3.0 cabin climate control is not working correctly anymore. During the cold days, it only blows cool air regardless of the temperature settings. On the warm days, only hot air out. AC is still working fine. I've searched the forum and found some threads talking about faulty condensation sensor, but don't know if it's related to my issue. Your help is greatly appreciated.

On older cars I would suspect that the thermostat is stuck in open (long loop) position... On a bimmer? hell, hard to tel...

does the engine run cooler than normal?

Engine runs normal, can feel engine heat after running for a while. During warm days, the air blows out warmer than outside air so I think the thermostat is okay.

Eliminate the most likely cause first...have you had your vehicle checked by an air conditioner specialist? It's entirely possible that your air conditioning system has a leak. Perhaps not very common but quite possible. First clue is usually warmer air out of one side and slightly cooler air out of the other (cooler air from vents closest to system inlet).

Yes. That was the first thing I did after reading some related issues cause by leaking AC system. The indy mechanic has confirmed no AC leaks. However, he could not figure out the causes and asked me to bring the car to BMW dealer. I just want to check with this forum to see if someone could help before bringing the car in.

As always this problem may be easier rectified by connecting the proper diagnostic equipment.There are a lot of air flaps regulating the air flow and if 1 or 2 are not in the correct position there is no other way to find that.Here is some good info:
http://www.bmwmotorsports.org/pdf/e7...%20Systems.pdf

Thank you bawareca for the link. It shows how complicated the climate system is. It is not easy for DIY to figure out without proper diagnostic equipment. I will find time to go to BMW dealer. Also thank you TerminatorX5 and mart_dev for your input. Really appreciated.