1999 Cavalier, Blower control issue

In this car that I just bought last week, I noticed that when I set the heater/vent to blow on my feet, it blows through all ports (feet, head, defrost). Out of curiosity, I moved the switch to the other settings and found this to be the case for all settings. I am not sure what is wrong. I believe the switch is bad, or the vacuum possibly, but I don't know how to check these things, so I am coming here for any help that can be provided. Swift response is appreciated, since I dont want to leave my dash in pieces for too long