Hmmm.. Mine work in the Auto mode. Haven't tried manual settings.

 

Is the air coming out of the “Face” and not “Foot” level? If it’s cold outside, maybe the heater is running so the automatic climate control is sending air the the floor.

 

Figured it out. Was trying to adjust them from the front seat and did not see the wheel to turn them on. Thought they were like the front ones where you slide them to turn it on.

 

I had the EXACT same experience. Also, in case anyone else comes looking: the rear vents follow the passenger face vent settings, if you're using different temperatures or if you have "driver only" on.