Hi all, just getting things going.
Here is my rendition of the air duct which feeds engine air from the fan to the crosspipe of the '89 Carrera heating system (the cross pipe feeds air to the air exchangers).
There is no fan in this as I put upgraded footwell fans (another thread I added to somwhere...forget where) with significantly stronger motors than the original Bosch pieces of junk.
I also rewired the autoheat fan control system so at low heat settings it is just the air from the engine fan (through this duct) and the footwell fans kick in only above level 3 on the autoheat control knob - with the standard 3 speeds, highest kicking in only at level 8, 9 and 10. The autoheat and AC control knobs were all standardized to use the autoheat knobs and relocated to my custom 3D printed console shown elsewhere on this thread.
This part is way too fun, lots of curves, had to master lofting in Fusion 360....several time I took the Lord's name in vain...sigh.
D.