Hi-
Not sure if your chassis is the same as a w123 but I solved all my blower issues by doing the following:
A: Replace brushes on motor (easy to pry end off motor and replace brushes)
B: Replaced motor speed control relay w/ used one from Pick-n-Pull (located behind glove box- above where motor is just under dash pad- it's a silver box- one of two)
C: Replaced temperature control module w/ used one from Pick-n-Pull (located next to other box- the 2nd box of two)
I did replace my climate control module (on dash w/ temp. selector & all the various buttons) before doing the above work but it didn't help at all. After more research I found that it's uncommon for these to fail.
Your chassis should have some, if not all, of these blower motor components.
Hope that helps somewhat.
Cheers!
-Chris