i just had the same problem in mine yesterday. i was putting the covers back on and thought i would test the fan first. mine didn't turn while hooked to a couple test wires on the batt. i took it the covers off around the motor and sprayed a quick squirt of WD40 in there and it runs fine now. how long???? who knows.
anyway, it's connected to a hose on the end which goes up to the little "grate" up by the courtesy light. it draws air from up there to the heater box to let the climate computer know what to do. yes, it is important.
roberto

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1985 300SD
1998 Jetta TDI
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