Yes, you can do that (wired to a switch) and it should work... to a point.
You'll probably encounter a couple of problems though, such as forgetting to turn it on (overheating), forgetting to turn it off (dead battery), and reduced cooling at anything over about 35mph.
To address the problem of the first two issues you might be tempted to hook it up to the ACC terminal, so it comes on only when the key is turned. That can work, but you'll need to do it with a relay, or risk blowing the fuse on the ACC terminal. That would also prevent you from running it with the engine off (to help cool down a really hot engine after a long drive) but that's not such a big deal.