Also, instead of going through a lot of things that may not take care of
the problem, just get some coins and tape them to the blade you suspect as
being

i spent hours trying to balance a 4 blade, 3 speed ceiling fan for my
parents using coins. never could balance "high" speed. i even swapped
blade positions. (motor with no blades was in perfect balance)

out of desperation, i measured the length and the weight of all 4
blades, all were identical. when i realized that different speeds was
the issue, it became obvious that pitch was causing the problem. a few
minutes later, with a protractor and string i found one blade bracket
had a 5 degree error to the other 3 blades. a quick "twist" to the
bracket to get it to the same angle as the rest was all it needed. the
fan now runs true at high speed (or any speed).

a trick to avoid the protractor- if the blades are gloss finish, put a
small light bulb a little higher or lower and behind the fan so you can
see it's reflection on the blades as they rotate. "twist" any errant
blade bracket, so that the bulb reflection is at exactly the same place
on all the blades. (spin by hand)

eye blade light bulb
) O
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-larry/dallas