When you turn on your AC, you should hear the clutch engage on the compressor, and you should see it spinning under the hood, if there is freon 12 in the system, the discharge side of the compressor going to the condensing coils by the radiator should be getting warm then to hot, the inlet side to the compressor should start to feeling cool, if there is no freon in the system, you will not feel any difference in the lines, which is usually the case, because the 'rubber' o-rings shrink and get hard and don't seal, usually about 10 years to 15 years roughly, if you had enough freon in the system and the compressor was working properly then any restriction in the high pressure side from the condensing coils to the orifice would be freezing up or frosty, past the orifice it should be getting cold to the evaporator coils in the car normally. A set of AC gauges is required to measure the low side and the high side pressures, and this helps to diagnose the system. If yours is like a factory system, it should have a york compressor, they are highly reliable but they can wear out and the front seal starts leaking. This should help diagnose it a little, post your results.