Donna -
I have had this problem for years on two different Imperials (a 64 and 67).
The problem seems to be that the clutch inside the motor housing sometimes
slips resulting in the situation where the motor turns but the window
doesn't.
Here's the fix that works for me. Don't do anything. That's right, my
problem windows "fix themselves" after a while. Go do something else and
then try it again and I'll bet the little guy works just fine. Sometimes
it takes a day or two, but it always works again and usually continues
working for months.
Ken Miller
61 and 67 Converts