AC problem

[BMMHT]

I've tried to find a thread that matches my problem but I havn't had any luck.So here we go. A/C would not blow cold , then start blowing cold driving down the road. Now it doesn't work at all .After checking some of the threads on here I checked some things.When the a/c button is on ,the compressor is kicked in and running,but the aux fan is not. I can unplug the inline ( what i believe to be) high pressure switch and the compressor stops and the aux fan comes on. Is it the switch or low freon ?