410-A system, low suction. 50psig discharge 240psig ambient. 75*F,unit icing up back to the compressor,evaporator iced,indoor coil encased in Sheetmetal, not accessible. What do I, do... TXV problem.

Suggest you repost this under "Home and Garden"-- heating and air conditioning. However, if you determine it is the TXV, you will need to open the plenum. Then you can install a slightly larger repair panel and use ductwork adhesive to seal it.