How I do it:
Put a big crescent wrench on the the fan clutch nut with the handle pointing to about 1:00 o'clock looking from the front. Hit the end with a hammer in a direction of 10:00 o'clock to 4:00 o'clock. The threads are left handed, i.e., from the front turn the nut clockwise to loosen it. Instead of righty-tighty, it's righty-loosey!