If I remember right, go in room where boss key is, then drop down and hookshot to the grate where the spinny thing was at boss key, lower yourself down as far as possible, then look north at the roof and hookshot the chandelier then put on iron boots. If fan is not off to lower down through, the go to boss key chest and shoot above at chandelier, then put on iron boots.

After you get boss key what do you do next to turn on the other fan to go to the boss door

I beet the game 10  or 11 times!!!!!!!