How do you know if your orifice tube is in need of replacing?

If the low side has too much pressure and the system isn't cooling properly that would be one sign that the orifice is plugged up. Removing the orifice tube and inspecting it would be the best way. If the orifice tube is loaded with metal trash, the compressor is probably on its way out. Replace the compressor, accumulator and orifice now before the compressor fills the system with trash, this you don't want to happen.