I just remembered something else that I have discovered on my own which I think I shared with other forum members?

89 300E AC-heater blower motor stopped after several months of some minor noise. This replacement is a several hour labor bill (read expensive) and the motor is high $$ too. Anyway--what I tried was moly assembly lube diluted with laquer thinner and the binding motor shaft became easy to spin again. Also I replaced the motor brushes with a larger set that a sanded down to correct size --- Cost $2 for the brush set at a local auto electric shop. I didn't think to inquire what the brushes were originally designed to fit ?? I posted some more details if anyone cares to do a search on "blower motor" it should come up. Blower is still doing fine and very quiet several months later. Saved several hundred on that job.... and it actually was not too bad, just don't force any of the trim pieces or the wiper assembly.

Luck to you , DanielW