I've had this 94 silverado 4x4 5.7 auto in storage for years and finally started driving it again, love it still.. 115,000 original and like new BUT the ac will ...

I've had this 94 silverado 4x4 5.7 auto in storage for years and finally started driving it again, love it still.. 115,000 original and like new BUT the ac will not work now. worked when parked so i thought low on freon, got some ac pro and it took some freon but thats it, clutch will not come on unless i disconnect the plug on what i think is the low pressure switch on the canister and jump it with a paper clip then the clutch comes right on so i replaced it and same thing ? will not take anymore freon, but made sure not to over fill.. i'm stuck! any idea's.. thanks