On the W123, space from housing to evaporator gets narrower from the blower motor opening as you go in further (wedge shape). Not sure if yours is the same. If same, be very careful so as not to crunch the fins with whatever tool you put in there. Inspecting with a borescope before and after cleaning is a good idea. An even better idea is to have the borescope attached to the cleaning "tool" so you can see what you are doing.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked