Recently the my ac has been coming in and out. A few weeks ago it would happen sporatically but as of this week it just won't come on anymore.

The econ light comes on and no matter how many times I press it the AC won't come on. Then I can drive for a bit and the AC kicks on on its' own. I know the ac has freon since on the times the ac kicks on it blows cold air.

 

could be either your compressor. OUCH $$$$ ooorr your ac high pressure switch could be faulty or loose.

 

I just had the same problem, had to get it replaced, approx 500$ job if you go to Audi.