Originally Posted by bman365
You need a blower motor resistor, which is on the bottom of the blower motor. That is, if your switch isn't bad.
This. The resistor is bypassed on the highest setting, which is why it only works there.
As for why it's hard to turn, I dunno but it's worth taking apart the center console to take a look. It's very easy to access - four screws and two wiring clips.