dc motors all operate on the same principal of M F C [motion,flux,current] you need any 2 to get the third,you have flux [perm magnet in motor]so you add current until motor gets to its full rpm. If you have wrong blower cage you might have too much load and never get to full rpm without drawing excessive current.The reason it wont pop a fuse on low/med is you have a resistor [that coil of wire thingy] that limits current.
