That is what I have an A/C shop that I trust to take my cars to. I do not have the gauges to measure pressure on the high and low side, which will tell you if the compressor is working, and that along with line temperatures and more training than I have, will help narrow down where the problem is. My '97 FDakota had a plugged orifice that I managed to diagnose because I had good pressure drop across the compressor, low suction pressure and the line coming out of the evaporator while cool was not cold, hence low overall flow. But that was an easy one. Usually if the dryer is plugged you have extremely low suction pressure and low discharge pressure because the compressor has nothing to work with. If you have no pressure difference across the compressor then there internal problems with the compressor. Requires gauge set and some understanding of the system and you can eliminate parts of the system. It is also possible to overcharge a system to the point that it loses it's effectiveness...you have to have the pressure difference across the expansion valve or there is no cool.
