Does the A/C compressor work? If you have too little refrigerant in the system, the compressor does not start/ does not start always.
If the fan direction does not work, iftmight also be the A/C control panel. Replacing it is easy. Open the center console, and you have access to the panel. I have written instructions here:
http://www.iki.fi/eerola/auto/MBC320Tdiy.html | Removing dashboard panels. New panels can be found in eBay.