I recently purchased a BMW 318ci with the Air Conditioning unit that has the 3 round dials.
I am selling my older car which is a 2001 BMW 318ci. The old car has the automatic push button Climate Control Unit. I have swapped them around but have found a problem.

The function that diverts the air from the vents to the windscreen to the footwell doesn't seem to work properly in either car when the A/C units are switched.

Can please someone let me know if there is a way to rectify this.