02 Protege5 A/C problem with vent controls

When I turn the vent control knob to the floor it turns on the ac compressor.

I know when the defrost is on it's suppose to turn on the compressor BUT it also NOW turn on for some strange reason when ONLY the floor is on ..

The A/C button DOES work and it not on..

Any ideas?

Have someone operate the controls inside and watch the compressor when they do so. The A/C button should turn the compressor on regardless of any other settings (fan should be on speed two or three). The compressor shouldn't turn on otherwise. The compressor will cycle on and off as the pressure rises and falls providing the button is turned on. If anything else is going on, then something very strange is wrong.