A/C problem, and Idle problem??? on 2000 Ford Contour

Okay, I'm going to ask both of my questions at one time: First question is, why does my car's a/c only work when it's on "hi"? Doesn't matter if it's heat or a/c actually, it's only blows out air on "hi", the reason I said a/c is because it's summer now. Next question is, when I'm driving, sometimes my car RPM will just "race" like it has a boost or something, it's not a bad thing, I think, I just want to make sure it isn't. Thanks!

Asked by for the 2000 Ford Contour
1 answer
For the air question is might be the blower motor resistor, its usually behind the glovebox near the blower motor. As far as the engine racing I really don't know.