putting coolent in ac.

there is no possible way to "show the ac is full" unless the system is evacuated and recycled so you will know the exact weight of the refrigerant. it is only "full" when the correct weight is in the system. after that, you need to know what the high and low pressure readings are, so that you will know if the compressor is "pumping". if these pressures are starting to equalize, then you have a weak compressor. a good general auto shop will have the proper test equipment and can likely give you a diagnosis at a reasonable price.