99 Grand Am internal fan problem?

Hello,

My car is 99 pontiac grand am V6 with about 87K.

I'd like to know what might be wrong when I turn to 1 or 2 of the fan setting, it doesn't work but it works on settings 3, 4, 5. Both heating and A/C works but since its on 3 at minimum, it gets really cold/hot really fast. I have to keep turning it on/off to have a comfortable temperature.

I guess my question is what could cause so that only certain settings (fan speed?) To work and not work? I'm assuming 1 and 2 are related or grouped together while 3, 4, and 5 is the other.

Thanks for any advice/ideas.