CVO 6/20/2012Check the radiator cooling fan and condenser fan ( if equipped ), they have to be ON in order to remove the heat from the A/C condenser.
Chris @ Motech 6/26/2012I agree with CVO. Check the fan. There are 2 speeds. The low speed should be on when the A/C is on. This is a common problem with these. If the problem has gone on for a while it can cause the A/C system to overpressure and bleed off the excess pressure (along with Freon). This will make the A/C work even less. Fix the fan first, if the A/C still sucks then check the charge on the A/C system.