[W126 Coupe] AC Blower not working

[Paul Samarin]

On my 1986 560 SEC:

The ac is working (I get cool air from the vents, which flows when I 
pop the sunroof up to create a slight draft), but the blower fan 
refuses to work in any of the 3 modes.  The 30A fuse outside of the 
fuse box was busted, so I replaced it and the fan worked again; then 
stopped.  That new fuse is still intact, but the #10 fuse in the fuse 
box was broken, so I replaced that one--no change.

It is very hot in So. Cal. these days.

What should I be checking next?

Thanks,

Paul