If you are sure of a full charge , look at sight glass and detect bubbles or liquid flow, pipes are cold on suction and hot on discharge ( smaller pipe) then you have a fan problem , evap coil getting cold but nothing to induce air over it. Check your fan for operation or restrictions , baffles not openning etc.
Or you may think it's getting cold but low on charge, ineficient, it will usually not allow the magnetic clutch to pull in on compressor by way of Low pressure switch.
Running our gasses on the standard pre 95 rubber tubing will eventually lose it's charge because of the smaller molecular structure of the modern gases in the older style hoses. Solution replace existing hoses with new or find some older R 12 refrigerant , but you will only find reluctant suppliers.