(This is concerning the vent right behind the center console)

Well I've had this issue since I got the X5 but I really didn't care before I never really had people seat in the back seats. But recently, I've had people in the back and it's been cold here in NY. They have complained that it's cold in the back but me in the front, I was totally okay. So I want to fix the vent issue.

I made sure the vent is open and switch on the hot. (red)

Maybe the air vent that the air travels through to the outlet got disconnected somehow.

Does anyone know how the ventilation system works or have had this problem and fixed it.

Thanks.