The fan draws/sucks in air at the rear view mirror grille. A test to see if the fan is functioning is to place a 1" square piece of paper near the grille and see if it gets sucked toward the grille.

A recent thread discussed disassembling and lubricating that sample fan to eliminate noisy operation. Never done it myself so I can't comment on the degree of difficulty, but you definitely want to repair/replace your fan ASAP so the Climate Control System works properly.

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Fred Hoelzle