AC not working - 2000 ZX2

The AC is not powering on. I think the problem may be related to the console control knob that turns on the AC, blower, and controls the vent flow. Though this control knob powers the blower motor off, the air flow comes out of the defroster regardless of the vent position chosen. Since the air vent settings are not functioning properly, I'm thinking that the control may not be turning the AC on either. In other words, the only thing working on this control knob is the blower off setting. I've driven several ZX2's, LS's, and SE's but have never seen this problem. Any suggestions?

Vent position is vac controlled if that vac line is disconnected or cut in any way the system automatically defaults to defrost for obvious safety reasons. The line is usually a small plastic vac line and it feeds into the firewall. As far as the A/C not working it could be a number of things, low/no freon, blown fuse, control head like you said, compressor coil, wiring.