How Do I Know If The System Under Or Over Charge Without Using The Gauge.

Make sure all fans are running and all covers are in place and condenser and evaporator coils are clear and all temperature controls set at their midpoints. To get the most accurate test as possible, the freezer must be cold. You want enough refrigerant in the system to flood the evaporator with liquid refrigerant, but not so much that the suction line begins to build frost or sweat. If the suction line (usually the larger of the two tubes) to the compressor starts to build frost or sweat, it's probably overcharged and should be reduced. Reduce charge extremely slowly until frost starts to back off. If the charge is too low, the frost pattern on the evaporator will not be complete and the unit will have to run way too long to attain setpoint temperatures. If the system is slightly overcharged, you may not know until after the freezer gets cold. Let it run for at least 1 to 2 hours before removing the evaporator cover to inspect frost pattern. During that time, watch for frost or sweat on the suction line back to the compressor. Of course, all of this is based on the assumption that you are trying to repair a standard residential refrigerator/freezer with forced air coils with electric defrost system, and all leaks have been repaired and leak checked, and filter/drier replaced. Good luck and let me know if you have additional questions.