97 Civic HX air always on

I'm driving a 1997 Honda Civic HX 2d wiht 160k miles on it. Runs great, but there is an annoyance. The air is always on, whether the fan slider is off or not. Oddly enough, the speed at which the air leaves the vents depends on your speed. So if you're stopped, no air. 75 mph, blasting wind.
It's summer now and I usually don't have the air on, as I enjoy to have my windows down. So this is a huge annoyance to have heat coming out of them. It's not hot if I have it set on cold, but it's still warm. Thanks