Does the 85 SD have a two speed aux fan with the lower speed triggered by the AC pressure switch? If so, maybe the problem with the aux fan is with a burned or corroded low speed resistor.

Have you confirmed whether it's only the blower fan that doesn't work or the ACC quite completely? You can check by pressing mode buttons and listening for the actuators to move, or set the temperature wheel to a min and check for continuous ground to the monovalve.

If only the blower doesn't work, did you note any axial play in the motor shaft? This indicates worn bearings. Even a little play can set the brushes away from their contacts. It doesn't help that the blower shaft is vertical. Sometimes setting the blower to max or kicking the blower housing gets the blower started. If so, your blower need more work than cleaning and lubing.

Sixto
87 300D