I'm a bit baffled by the climate controls in my M20 E34 (wow, learning the lingo already). Here's what it looks like:



Sometimes, when I turn both knobs to full heat, the two vents in the center won't blow the same air. One will blow hot and one will blow cool. Does this have anything to do with the red-blue slider between the two vents? I dont understand what it does.

Also, on the blower, what is the fan speed before "1" supposed to do? It seems to be on, but blowing very gently at the same speed no matter where I set it. Could buildup behind my evaporator be preventing the fan from blowing more air?

Thank you!
-Jesda