air conditioning problems

i cant get my air conditioning or vent to work. when i turn the knob all the way to cold and put the air or vent on its all heat. i dont know what the problem is so if anyone can help me it would be great. :banghead:

compressor is not kicking on. That could be for many reasons, the most common is that their is not enough r-134a to set off the pressure switch. The next common thing is that the compressor clutch is not working. unplug the harness to the high pressure switch and with the car running and the AC on use a wire to short the termanials in the harness (Not the pressure switch) if the compressor kicks on then you know the clutch works. Don't let it run for long if it does kick on. That test will tell you one of two things, 1 you don't have enought pressure in your AC system, 2. You have bad pressure switches. More than likly you just need a recharge.